The Council of Chalcedon did NOT endorse the Three Chapters. It merely did not bother to condemn them.
I'm sorry Linus, but you miss the point. The West DID believe that the council of Chalcedon endorsed the Three Chapters. There is a mountain of primary evidence to show this is the case. What matters in this context is not what happened but what the perception was of what happened. The West believed that Chalcedon had accepted the Three Chapters.
It was the Western Chalcedonians who insisted that the letter of Ibas had been received.
This is just history. It is beyond revisionism.
Why did Facundus, the senior North African bishop and theologian, end his life in prison for insisting that Chalcedon had accepted the Three Chapters if this was not the tradition of his Church? It certainly wasn't something he made up. He believed it to be true. So did all his fellow bishops since they all went into schism from Pelagius. So did all of Gaul. Indeed parts of Gaul remained in schism over the matter until 700 AD. They insisted that the tradition of the Church had always been the Chalcedon had accepted the Three Chapters.
They may have been wrong.
But that is what they believed. Therefore it is not reasonable to say that the Non-Chalcedonians were unreasonable in asserting that the Three Chapters had been received at Chalcedon. There were plenty of Chalcedonians insisting on the same thing.
And as for Ibas' letter. I think you are only using the much edited and abbreviated CCEL edition of the Acts which misses most of the Acts out. The Catholic Encyclopaedia, a source I know you trust, says:
"At the Council of Chalcedon the Patriarch Maximus of Antioch and the Roman legates declared: "Having read his letter again, we declare that he is orthodox."
How could anyone read his letter and declare him Orthodox? Let us see what Constantinople II says about the letter:
"In the third place the letter which is said to have been written by Ibas to Maris the Persian, was brought forward for examination, and we found that it, too, should be read. When it was read immediately its impiety was manifest to all."
Now how can the one council read the letter and declare on the basis of it that Ibas was Orthodox, and
the latter council read the letter and declare that its impiety is obvious to all?
I have not misquoted the legates, as the quote from the Cath. Enc. shows. The letter was read and with that in mind Ibas was declared Orthodox.
This seems a reasonable question.
Again, the Cath. Enc. also states that resistance to any condemnation of the Three Chapters was the general position in the West:
"The bishops of Aquileia, Milan, and of the Istrian pennisula all refused to condemn the Three Chapters, and excommunicated the Popes for their subscription. Since these bishops were subjects of the Lombards, they were beyond the reach of both the Pope and the Exarch at Ravenna, and maintained their dissent into the 7th century. The see of Milan renewed communion with Rome when its bishop Fronto died about 581. As he had fled from the Lombards to refuge at Genoa, his successor was dependent upon the Byzantines for support, and was induced to subscribe to the condemnation.
On the death of Severus, the Archbishop of Aquileia in 607, the Byzantines made a vain attempt to install a favorable prelate in that office, which only severed to deep the schism along Lombard-Roman lines. Columbanus was involved in the first attempt to resolve this division through mediation in 613.
The remaining primates ended the schism only after the Lombards embraced Catholicism in the 7th century, formally at the Synod of Aquileia in 698. This extended period of independence contributed to the evolution of the independent Patriarch of Venice from the Archbishop of Aquileia."
It is also a reasonable question to ask what standing Father John Romanides has in Eastern Orthodoxy since on the one hand he is referenced in many of the EO books I read as an authority, yet here he is condemned as being a false teacher. I can assure you that all the quotations are taken directly from his own website.