Yes, there were Pharisees who accepted Christ and they may have been Bereans who did not.
The Lord chose to bring forth fruit through the Pharisee, Paul.
On the other hand, a careful reading of the New Testament shows that it supports Catholic and Orthodox practice of using the LXX as the basis the Old Testament canon.
That's that Papal myth again. If that was the accepted practice then the tradition would not have multiple canons, including the thirty nine, among the Greek speakers of the undivided Church of the Roman Empire.
There was no recognized canon among the Jews at the time of Christ,
So is it your claim that the Jews had no idea what Jesus meant when He referred to the law and the prophets? That is a silly idea considering that not one apostolic witness took the time to define it for the Jews or for the Gentiles who were coming to the faith.
and the New Testament did not exist in its current form until hundreds of years later.
That is a story unless you only mean that some books of the now commonly accepted NT canon weren't commonly and formally recognized until centuries later.
The earliest Christian bible was the Greek Old Testament used by the Bereans and Timothy's family since that was the language of the New Testament and the international language of the eastern Roman Empire.
That is again a Papal mythological revision of history. Makng use of some of the language of a pre-existing translation says that the language of the translation is adequate in those instances. It says nothing about what is or is not canonical as the later confusion of the Greek speakers of the one Church of the Roman Empire went on to demonstrate through their use and sanction of multiple OT canons.
The apostles did not accept the modern doctrine of sola scriptura since they never explicitly defined the canon for the Old Testament, and much of the New Testament was not written until after the death of most of the apostles.
That is false. Christ told the unbelievers to search the Scriptures because they testify of Him. He didn't say search your heart for a burning bosom, consult the soothe sayer down the road, consult the high priest or the scribes and Pharisees, read the tea leaves, etc., for a true testimony of Him
On the other hand, it is clear that the apostles favored the version of the Old Testament used by Greek-speaking Jews over that used by the Pharisees in Judea.
That is just the same tired Papal myth in this regard because using the common language of those with whom you are trying to communicate isn't a statement regarding the extent of the canon.
Fore example consider Acts 15, when they specifically quoted an Amos LXX verse that is much different than that used in modern Hebrew scriptures.
You weren't specific, but if you referring to the verse actually quoted from Amos, 9:11, I don't see a substantive difference. If you are referring to the context in which it was used, provided, by Acts 15::17, then there is no verifiable evidence for your claim. In other words, without a copy of Amos which predates Acts there is no way to tell if the translation, the LXX, was revised to match Acts 15:17.
They quoted the verse in response to a dispute between Pharisee Christians from Judea and Greek-speaking Christians from outside of Judea.
It is agreed that Acts 15 is an accurate record of what occurred, but there is no evidence to support your claim that Acts 15:17 quotes Amos 9:12 from the LXX rather than Amos in the LXX being revised to match Acts 15:17.
Verses among those most frequently used as proof texts for sola scriptura (Acts 17:11 and 2 Tim 3:15) actually support the authority of the Greek Old Testament since that is version that is specifically praised.
That is an assumption. Since they went to the synagogue of the Jews we don't know if the Scriptures they checked were the Targumim, Hebrew, or the LXX.
The Catholic Old Testament canon is consistent with the New Testament.
There is no verifiable evidence that the Papal OT canon is consistent with the NT. It is even worse when one considers the content of the Papal translation of the LXX, for example, see Sirach 1:18 which is a fabrication teaching false doctrine. If you want to stick with the content of the LXX then other examples can be found.