Until I read this I thought Hebrew and Jewish would have been used interchangeably in this context. Apparently not. Would you provide some more information about this? I know there is the Samaritan group which practiced a religion related to Judaism. Were they Hebrews but not Jews?
I just looked up Hebrews in Wikipedia and my head is spinning. The term seems to not mean exactly Jew except in a bunch of languages other than English where it means exactly Jew. The term seems to have various meanings throughout history, but I suppose the part of all this that supports you idea is that often the term was used in a way that was not synonymous with Jew.
I'm not exactly an expert on all this, but the main gist I get from reading Eisenman is that Paul was very clever with words. He knew all the rhetorical tricks in the book and used them cleverly. When it comes to describing himself he never actually uses the word "Jew" (or the greek equivalent), but he uses these convoluted phrases whereby his audience can infer that he is Jewish without him actually saying it. I think of him as a shifty Lawyer type who deceives people by very carefully not lying.
He has no qualms about calling Peter a Jew and calling the Jewish people "cursed" by the Laws of Moses, but he says he is free to act as either a Gentile or a Jew whenever it suits his purposes.
He also repeatedly states that he isn't a liar, which makes me think that someone must have been accusing him of lying. Then when you read what the DSS have to say about the "Spouter Of Lies who preached against the Law in the midst of the congregation", Paul would seem to be a prime candidate.
Then we also see how Acts has him associating with Simeon Niger and Menachem (Menaen) at Antioch and see how those people were aligned with Herod during the revolt against Rome, a picture of a herodian "Controlled Opposition" doesn't look too far fetched, at least to me.