Actually, you should to read more research about the so-called "Council of Jamnia." as well as the LXX.
If your point is to argue that there was a Jewish canon set long before Jamnia, the proliferation of both non-canonical and incomplete Bible texts should immediately rebut that, as well as Jesus referring to texts not accepted by Jamnia more than a dozen times as “scripture.”
In fact, there are three canons referenced by Jesus, “the law,” “the prophets and the law” and “scripture” and none of these three is at all similar to the canon that was known after Jamnia as the Jewish bible. Today, “the law,” “the prophets” and “the scripture” give their names to the initialization “the TaNaKh,” but we know that the “K” part of the Tanakh, the “Ketuvim” is not the same canon as “the scripture” because of the many times Jesus cites scriptures which are not in the Ketuvim. To those whom Jesus appeals to “the law,” Jesus reports that they deny the prophets.