Correction, radiocarbon dating of the Gospel of Judas fragments are between 220 and 340 AD.
"Wrong! The Gospel of Thomas Greek manuscript fragments have been dated to 200AD and the Coptic version to 340AD. The Gospel of Judas has been dated 130 to 170AD. These are much later than the original New Testament books."
Paul was battling the writings and teachings of the Gnostics long before the manuscripts you speak of. But your point is a fine line between what was taught and when the manuscripts were composed.
But that is a good point to consider...does the fact that St John did not write Revelation or the Gospel of John until around 95AD invalidate all that was being taught by word and tradition since 33AD?
Even the Gospel of Matthew wasn't written until after 50AD. Again, to the early Christians, it was not the books but the teaching, the Holy Spirit alive and working in the Apostles, and the traditions being handed down by word of mouth.
Those books you mention, were declared to be NON-CANONICAL, by the Undivided Church.
That is the end of the story, as far as I am concerned.