To return to this post.
I don’t think Paul has abandoned Jesus’ Jewishness (or for that matter, Jewishness by itself), if by that you’re claiming that the earliest Christian controversy between the Jewish Christians and the gentile Christians revolved on the issue of Jesus’ identity or divinity. Because that was not the issue.
The controversy was rather about whether baptized gentiles should become Jews first in order to become ‘full’ Christians. As you know, those whom Paul called ‘Judaizers’ argued that gentiles must be circumcised in order to really become followers of Jesus: Torah observance is seen as obligatory.
Paul as mentioned however no longer saw the Torah as obligatory. It is no longer binding on everybody now that Jesus had come and inaugurated a new age. To say that Torah observance is still obligatory for salvation, he argued, questioned the sufficiency of Jesus. Now, “apart from the Law, the righteousness of God has been disclosed” in Jesus (Romans 3:21), and he is now the revelation that must be acknowledged in trust/faith. At the same time, however, Paul still affirms the Torah as a genuine revelation of God. For example, he rhetorically asks whether this new development (Jesus) overthrows the law - to which his immediate response is an emphatic “Absolutely not!” (Romans 3:31). He also saw the Jewish people as still having a significance in God’s plan (e.g., Romans 9-11).
At best, Torah observance was still an option for Jews like himself, as a cultural marker of their identity as Jews. If you’re a Jew, you could still follow the Law if you wanted to, just so long as you did not try to impose it on everybody else (non-Jews much more so), because in a post-resurrected Jesus age it is no longer the requirement to have a relationship with God - Jesus is now that new requirement.
AFAIK nowhere does Paul in his letters insinuate that Jewish believers in Jesus must forsake the Torah, contrary to what his opponents insinuated. In fact, in Acts 16:1-3, Paul has Timothy circumcised, apparently because his mother was Jewish and so he (Timothy) counts as a Jew. So it’s not as if Paul had a problem with circumcision itself, or even circumcising Jewish believers. It is the idea of gentiles having to be circumcised that he had a problem with. At best, you could accuse Paul of being too lenient to the non-Jews, but IMHO you can’t really accuse him of abandoning Judaism wholesale.
In fact, it’s not even Paul vs. James and Peter on this issue, at least at first. It was actually more like Paul and Peter vs. James. Peter apparently wavered when he and Barnabas refrained from eating with gentiles at the presence of the ‘Judaizers’ (effectively doing something that could be construed as denying the non-Jewish converts that they are somehow ‘not Christian enough’), which led to Paul upbraiding him in public.