Since SGI is wrong about the identity and nature of the Eternal Buddha why would you believe it is correct about anything else?

The entire thrust of the Rissho Ankoku Ron is that the Treasure of the Buddha is Shakyamuni and the Treasure of the Law is Myoho renge kyo (Lotus Sutra). 

Nichiren says in "Reply to Lady Nichinyo": "I for the first time reveal, as a banner of the spread of the Hokkekyo the Great Mandala which even Nagarjuna, Vasubandhu, and so on, and Tendai, Myoraku, and so on did not reveal. This is not at all something which I, Nichiren made myself. It is the Object of Worship which is from the print block of the Great Muni, the World Honored One within the Stupa of Taho and the Separate-Body Buddhas." 

                

Clearly, the Daishonin inscribed the Gohonzon as taught to him by the Great Muni. 

"Thus it was revealed that Shakyamuni had long been the Buddha since the eternal past, and it became clear that various Buddhas in other worlds were all manifestations of Shakyamuni Buddha..[ ] now, however, as Shakyamuni was proved to be the Eternal Buddha, those Buddhas in the Flower Garland Sutra, or Buddhas in the Hodo, Hannya, or Great Sun Buddha sutras all became subordinates of Shakyamuni Buddha."  (Kaimoku Sho, p. 174, translated by Kyotsu Hori, 1987) 

Same quote in the MW's: 

"When Shakyamuni Buddha revealed that he had gained enlightenment in the far distant past and had since then been constantly in the world, it became apparent that all the other Buddhas were emanations of Shakyamuni....but now it became apparent that Vairocana Buddha of the Kegon Sutra and various Buddhas of the Hodo, Hannya and Dainichi sutras are in fact all followers of Shakyamuni Buddha."  (MW V.2, p.149) 

        

"But now since it has been revealed that Shakyamuni is the Eternal Buddha....etc."(Kaimoku Sho, translated by Kyotsu Hori) 

"...Shakyamuni Buddha, within our minds, is an ancient Buddha without beginning, manifesting Himself in three bodies, he attained Buddhahood n the eternal past......( Kanjin Honzon Sho, translated by Kyotsu Hori  P.94) 

"...the Bodhisattvas (who sprang from underneath the ground), as described in the 15th chapter, are followers of the Original Buddha Shakaymuni who resides within our minds."(Ibid pg 94) 

"The "honzon" at the scene of this transmission of "Namu Myo Ho Renge Kyo" from the Eternal Buddha to His Original Disciples is....suspended in the sky above the Eternal Buddha Shakyamuni's Saha-world is a stupa of treasures, in which Shakyamuni Buddha and Taho sit to the left and right of "Myo Ho Renge Kyo". (ibid. 

P.102)  

"Since Sakyamuni Buddha is eternal and all other Buddhas in the universe are His manifestations, then those great bodhisattvas converted by manifested Buddhas are also disciples of Lord Sakyamuni Buddha.  If the "Life Span of the Buddha" chapter had not been expounded, it would be like the sky without the sun and moon, a country without a king, mountains and rivers without gems, or a man without a soul. (Noppa, pg. 176, Kaimoku Sho)" 

and from Kanjin Honzon-Sho  (NOPPA) page 56 

"In fact Sakyamuni began to preach, planting the seed of Buddhahood in the eternal past... Sakyamuni Buddha continued to guide His disciples until they were all sure to attain Buddhahood during the preaching of the Lotus Sutra in His present life, completing the series of His preaching which began in the eternal past." 

and

"This means that Sakyamuni Buddha, Taho Buddha, and all the Buddhas in  manifestation are in our minds, and that we, upholders of the Lotus Sutra, will follow in their steps and inherit all the merits of those Buddhas." 

"It means that Sakyamuni Buddha, within our minds, is an ancient Buddha without beginning, manifesting Himself in three bodies, and attaining Buddhahood in the eternal past  described as 500 dust-particle kalpa ago. 

"In the same chapter, another passage reads: ‘The duration of My Life, which I obtained through the practice of the way of bodhisattvas, has not yet expired.  It is twice as long as the length of time stated above: 500 dust-particle kalpa.’  This reveals the bodhisattva-realm within our minds. The bodhisattvas described in the fifteenth chapter, ‘Appearance of Bodhisattvas from Underground,’ who have sprung out of the great earth, as numerous as the number of dust-particles of 1,000 worlds, are followers of the Original Buddha Sakyamuni who resides within our minds." 

Kanjin Honzon-Sho  (NOPPA) page 94: 

"Now , when the Eternal Buddha was revealed in the essential section of the Lotus Sutra, this world of endurance (Saha-world) became the Eternal Pure Land, indestructible even by the three calamities of conflagration, flooding, and strong winds, which are said to destroy the world.  It transcends the four periods of cosmic change: the kalpa of construction, continuance, destruction and emptiness.   Sakyamuni Buddha, the Lord-preacher of this pure land, has never died in the past, nor will He be born in the future.  He exists forever throughout the past present and

future.  All those who receive His guidance are one with this Eternal Buddha." 

            

"Nevertheless, the sects of Buddhism other than Tendai have gone astray concerning the true object of worship. The Kusha, Jojitsu, and Ritsu sects take as their object of worship the Shakyamuni buddha who elliminated illusions by practicing thirty-four kinds of spiritual purification. This is comparable to a situation in which the heir apparent of the supreme ruler of a state mistakenly believes himself to be the son of a commoner. The four sects of kegon, Shingon, Sanron, and hosso are all Mahayana schools of buddhism. among them the Hosso and Sanron sects worship a Buddha who is comparable to the Buddha in the superior -property-of-action aspect. This is like the heir of the supreme ruler supposing that his father was a member of the samurai class The Kegon and Shingon sects look down upon Shakyamuni buddha and declare that Mahavairochana or Dainichi buddha should be the true object of worship. This is like the heir looking down upon his own father, the supreme ruler, and paying honor to one who is not even related to him by blood simply because that person pretends to be the Dharma king.

The Jodo sect considers itself to be most closely related to the buddha Amida, who is an emanation of Shakyamuni, and rejects Shakyamuni himself. The Zen sect behaves like a person of low birth who makes much of his own achievments and despises his father and mother...."

Kaimoku Sho: 

            

The men of these sects who are ignorant of the teachings of the Juryo Chapter are similarly like beasts...." 

In the Nirvana Sutra, Bodhisattva Kasho posed thirty-six questions to the Buddha, but even these cannot compare to the question concerning the bodhisattvas who appeared from the earth.  If the Buddha had failed to dispel the doubts concerning this matter, the sacred teachings of his entire lifetime would have amounted to no more than froth on the water, and the members of the multitude would have remained tangled in the snare of doubt. That was why is was so important for him to preach the Juryo chapter.   

Later, when the Buddha preached the Juryo chapter, he said:  "All the human and heavenly beings and the ashuras at present believe that Shakyamuni Buddha, after leaving the palace of the Shakyas, sat in the place of meditation not far from the city of Gaya and there attained the supreme enlightenment."  This passage expresses the view held by all the great bodhisattvas from the time when Shakyamuni first attaned enlightement until the preaching of the Anrakugyo chapter of the Lotus Sutra.  "However, men of devout faith," the Buddha continued, "the time is limitless and boundless -- a hundred, thousand, ten thousand, hundred thousand, nayuta aeons since I in fact attained Buddhahood." 

Three places in the Kegon Sutra the Buddha said: "I have attained enlightenment for the first time in India."  In the Agon sutras he speaks of having "for the first time attained enlightenment"; in the Vimalakirti Sutra he says, "For the first time the Buddha sat beneath the tree"; in the Daijuku Sutra, "It is sixteen years since the Buddha first attained enlightenment"; in the Dainichi Sutra, "Some years ago when I sat in the place of meditation"; in the Ninno Sutra, "twenty-nine years since my enlightenment"; in the Muryogi Sutra, "previously I went to the place of meditation"; and in the Hoben chapter of the Lotus Sutra, "when I first say in the place of meditation."  But now all these passages have been exposed as gross falsehoods by this single pronouncement in the Juryo chapter. 

When Shakyamuni Buddha revealed that he had gained enlightment in the far distant past and had since then been constantly in the world, it became apparent that all the other Buddhas were emanations of Shakyamuni.  When the Buddha preached the earlier sutras and the theoretical chapters of the Lotus Sutra, the other Buddhas present were pictured as practicing various religious austerities and disciplines side by side with Shakyamuni Buddha.

Therefore the people who pay devotion to one or another of these Buddhas as the object of worship customarily look down on Shakyamuni Buddha.  But now it becomes apparent that Vairochana Buddha of the Kegon Sutra and the various Buddhas of the Hodo, Hannya and Dainichi sutras are all in fact followers of Shakyamuni Buddha.   

When Shakyamuni gained enlightenment at the age of thirty, he seized the saha world away from Bonten and the Devil of the Sixth Heaven, who had ruled it previously, and made it his own.  In the earlier sutras and the theoretical of the Lotus Sutra, he called the regions of the ten directions "pure lands" and spoke of the present worlds as an "impure land."  But now he has reversed this in the Juryo chapter, revealing that this world is the true land and the so-called pure lands of the ten directions are impure lands, mere provisional lands. [The Opening of the Eyes, MW Vol.2, pages 148-150]

"If Shakyamuni Buddha had actually attained enlightenment for the first time at the age of thirty, then when he preached the Lotus Sutra, Bonten, Taishaku, the gods of the sun and moon and the Four Heavenly Kings who have ruled the present world from countless ages in the past would have been disciples of Shakyamuni Buddha for no longer than a period of forty-some years.  During the eight years when he preached the Lotus Sutra, the beings who assembled to listen to him would have been unable to accept as their master a person who had so recently come to prominence and would have deferred instead to Bonten, Taishaku and the other deities who had from ages past been the lords of this world.   

But now that it has become apparent that Shakyamuni Buddha attaine enlightenment countless aeons ago, then the Bodhisattvas Nikko and Gakko, who attend the Buddha Yakushi of the eastern region, the Bodhisattvas Kannon and Seishi, who attend the Buddha Amida of the western region, along with the disciples of all the Buddhas of the worlds of the ten direction and the great bodhisattvas who are disciples of the Buddha Dainichi as they are shown in the Dainichi and Kongocho sutras --- all of these beings are disciples of Shakyamuni Buddha.  Since the various Buddhas themselves are emanations of Shakyamuni Buddha, it goes without saying that their disciples must be disciples of Shakyamuni.  And of course the various deities of the sun, moon and stars, who have dwelt in this world from countless ages in the past, must likewise be disciples of Shakyamuni Buddha.  [The Opening of the Eyes, MW Vol.2, pages 151-152]

From the Hoon Sho, Kempon Hokke Seiten:  

".... Japan and so on to the whole of Jambudvipa should uniformly take the Master of Teachings Lord Shakya of the Original doctrine as the Object of Worship".  

In the Kanjin-honzon-sho it says: 

"During the fifty years of his teaching from the time of his enlightenment under the Bodhi tree till his Parinirvana under the Salatree, the Buddha expounded many sutras. In these sutras he described a wide variety of pure lands, such as the Pure Land of Flower-Store, the Pure Land of Esoteric Adornment, the Pure Land of ThreeTransformations, the Pure Land of Peaceful Life, and the Pure Land of Emerald. These pure lands are either the abodes of the followers of the Lesser Vehicle, or of the partially-enlightened Bodhisattvas, or of the perfectly enlightened Bodisattvas.These pure lands are, however, impermanent. They are established on in the kalpa of composition. The expounder of these sutras is the historical Buddha, and the Buddhas of these pure lands are the manifestations of the historical Buddha.

Therefore, when the historical Buddha enters into Parinirvana, the Buddhas of these pure lands pass away, and their pure lands also disappear. But the Saha-World of the Original Buddha is the eternal pure land, free from the three calamities and the four kalpas. In this eternal world the Buddha never disappeared in the past, nor is to appear in the future. All living beings under him are one with him because they have the wisdom of the Buddha in their minds." 

"Having had doubts about the matter, I consulted the passages of the Lotus Sutra, and they reveal why this object of worship has never before appeared. The sutra clearly states that it should not be established before the predicted age of conflict in the Latter Day of the Law.  Those Buddhist scholars and teachers who appeared in this world during the Former and Middle Days of the Law did not establish this object of worship because they honored the Buddha's prohibition.  Had an object of worship of Lord Shakyamuni who attained enlightenment countless aeons before and his attendants ever been made during the Former and Middle Days, it would have been like the sun appearing at night or the moon shining by day Because Bodhisattva Jogyo will establish this object of worship in the first five hundred years of the Latter Day, those four ranks of scholars and teachers who appeared during the Former and Middle Days did not even describe it in words.  

Nagarjuna and Vasubandhu knew of it in their hearts but did not speak to others about it. The Great Teacher T'ien-t'ai Chih-che also knew of it, but, as he was bodhisattva of the theoretical teaching, though he taught it in part, he did not expound its true meaning. He taught it indistinctly, like the cry of a cuckoo which one hears just before waking from a dream. Other Buddhist teachers did not say so much as a single word about it. For at Eagle Peak, Shakyamuni Buddha strictly prohibited those scholars and  teachers who were bodhisattvas of the theoretical teaching, and who would appear during the two thousand years of the Former and Middle Days, from disclosing even indirectly prior to the Latter Day anything about Lord Shakyamuni of the essential teaching who attained enlightenment in the remote past and the four Bodhisattvas of the Earth led by Jogyo who have accompanied him ever since."(Major Writings, Nichiren Daishonin, Volume 3, pages 293, 294, 295, Four Bodhisattvas.) 

           

Since SGI is wrong about such a crucial and obvious point why would you think it is not mistaken about such doctrines as the role of shoju [peaceful practices] and shakabuku [forceful practices], transmission through a sole heir, the master-disciple relationship, actual proof, the role of priests etc. etc.?