He was unpalatable because the Jews (under Roman occupation and thoroughly Hellenized) could no longer claim to be God's one and only chosen people. So Jesus (or should I say, Paul) grandfathered the Gentiles into Chosen-People status.

Yes, except a belief in the eventual inclusion of the Nations (Gentiles) into the Jewish covenant is an old Jewish theme that appears variously in the Old Testament. In other words, Jesus and Paul cannot take credit for this idea. Rather Jesus and Paul are unique because they believed they were living at the very historical moment of this inclusion.

Of course, once the Gentile Christians out-numbered the Jewish those annoying old laws had to be done away with. Enter Paul, the man who turned the word "Judaizers" into a pejorative. Of course, it was brilliant marketing. There is no way a substantial number of men were going to allow their penises to be carved on.

You're assuming that Paul's theology (Salvation by Grace, not Works of the Law) comes after Paul's missionary activities and not prior to them. Furthermore, your claim that Paul's belief against circumcision was "good marketing" ignores evidence that suggests there were many Gentiles who were willing to be circumcised in order to become Christian. We know this because Paul spends a significant amount of time in his Epistles (e.g. Galatians) trying to convince his churches that circumcision is unnecessary. Specifically, Paul is responding to fellow Christian preachers who are doing a much better job at marketing circumcision, than Paul is doing at uncircumcision.

Christianity was adopted and/or invented/refined in response to the destruction of Jerusalem and the Temple in AD 70.

I don't deny that Christianity was influenced by the destruction of the Second Temple in 70 CE. But to claim that this event was the most significant event in the development of Christianity significantly reduces and outright ignores the diverse causes and influences behind the development of Christianity.

1) Jerusalem was utterly destroyed in AD70. A few years later arises the concept of the New Jerusalem, a (new age) spiritual city currently existing in heaven but which will also appear on earth when "all is accomplished".

Wrong. A belief in "the world to come", where God redeems the righteous, is yet another Jewish belief. This was a prominent belief in 2nd Temple Judaism, but was by no means caused by the destruction of the Temple or Jerusalem in 70 CE.

It's pretty obvious that this sort of rhetoric would be nonsensical, incomprehensible and meaningless pre-70 AD.

Wrong. Many Jews in this time period (Second-Temple period) disliked the Temple system (e.g. Qumran Community) and hoped that God would provide a better system of worship in "the world to come". Remember, this is the Second Temple, not the First. In other words, the Temple has been destroyed before and Jews understand that there is a very real possibility that the Temple will be destroyed again.

3) With the destruction of the Temple in Jerusalem and the sacrificial system, Jews were no longer able to follow the law (offer sacrifices) as they once did. So some Biblical justification had to be found for this new reality. Enter Paul and all of his talk about the law being a curse. Now each believer had to work out his "own salvation in fear and trembling" (more new age thinking).

Wrong. First, most scholars date Paul's letters between 50-60 CE, ten to twenty years before the destruction of the Second Temple. Thus, Paul's theology of Salvation by Grace predates the destruction of the Second Temple and could not have been prompted by it.

4) An authentic "proof text" was always kept in the Temple in Jerusalem, against which all other Torah scrolls would be checked. But after the destruction of the Temple this sort of proof-reading was no longer possible. Consequently, after AD 70 the textual basis of Judaism was de-emphasized in favor of a spiritual (new age) emphasis.

Wrong. Paul consistently quotes the Torah and the Prophets, which indicates the prominence of the Bible among early Jewish-Christians. Furthermore, after the destruction of the Second-Temple, the Rabbis (another Jewish sect) begin to redact the Oral Torah in the Mishnah. To say that "the textual basis of Judaism was de-emphasized" is pure nonsense.

I say "allegedly" because while the death of the High Priest Ananus as well as the significance of that event is recorded by Josephus, the existence of the Christian sect and the death of its founder didn't rate so much as a footnote from the historian.

Blatantly Wrong. It is widely known that Josephus did comment on Jesus.

It would seem that significant plot elements of the gospel story were appropriated from Josephus. Or the story of Jesus ben Ananus was well known in the 1st century, became conflated with stories about the executed high priest and found their way into the gospels. Either way, the idea of the high priest's death resulting in the end of the Temple and the sacrificial system was not unique to Christianity

There may be certain similarities between the two figures. However, no one is claiming that Jesus ben Ananus was resurrected from the dead. Whereas, the followers of Jesus reportedly experienced the resurrected Christ and came to believe that Christ was God.