Lastly, regarding Acts 21. I have, of course, read it many times. The fact that Paul was willing to pay the expenses to end the vow, aka to prove he kept the law may simply be his willingness to do what he said he was willing to do..."be all things to all people."
Let's get back to the discussion. You say you've read Acts 21. Now, Acts 21 says:
"Then everyone will know there is no truth in these reports about you, but that you yourself are living in obedience to the law."
So here's our options:
(1) Paul intentionally deceived the council, pretending to be obedient to the law when, in reality, he was against the law;
(2) Paul was truthful.
So let me ask you: do you think Paul was a liar?
"In chapters 2-5, the objective is not to prove that Paul was a Torah-observant Jew (this is beyond the scope of this study and perhaps the available evidence)," (pg. 18 of "A Jew to the Jews" by David Rudolph).
In reality, Acts 21 contains evidence that conclusively establishes that Paul was a Torah-observant Jew.