Andrew, to respond to your numbered points:

1. My view is that the over-arching concern of the NT canon is with a change of covenant and all of its intricate implications for a community that is defined by that relationship…rather than a prophetic warning of coming destruction. Nevertheless, I hold your concerns about the destruction of Jerusalem in tension with the principal concern I recognise. (I’m not convinced that it should have the profile you appear to give it by your apparently pedantic devotion to it. But I accept that is the nature of developing an apologetic—in another context, your argument might find a more obviously appropriate ‘gravity’.)
2. I’m not convinced by this dialectic, Andrew. It seems to me that within the Hebrew and NT canon, blessing is inevitably associated with covenant. I wonder if you might be guilty of looking back from a modern viewpoint in this regard and retrojecting a notion of blessing that didn’t exist in the first-century…but perhaps you can cite authorities that support the view?
   • Regarding OT thought about being a priestly people in the midst of Gentile nations…A reasonable suggestion, but Paul certainly transforms this element of prophetic vocation in Romans 15.16, whereby the priestly role is explicitly linked with "gathering in the Gentiles." through proclamation of the Good News. You may suggest that Peter was behind the times (again; poor old Peter, when does he ever catch up?), but in so doing, you might appear to be hinging more and more of your argument on Peter’s intransigence of thought / lack of revelation compared to Paul—but I don’t want to put words in your mouth!
   • Regarding Acts 10/11: in truth, I have some sympathy with reading in the text the notion that Peter (God bless him) was slow to recognise that the Gentiles were now welcome in covenant community; however, I would suggest it is nevertheless, possible to read the text as I originally suggested. In Acts 10.47, Peter stops to ask whether any of those present (known to include those devoted to circumcision, v.45) would stop the Gentiles being baptised now they had received the Spirit. He has certainly understood by now (at last!) that the Gentiles are being brought into the kingdom; his final note of reticence is surely concerned with whether it is now right to allow them baptism—indicating entry to the Messianic / New Covenant Community—without circumcision…
   • Furthermore, the surprise you refer to, of those to whom Peter reports, does not necessarily indicate what you suggest. They are not remarking, "Wow, the great unwashed are now welcome! Amazing" Rather, Gentiles were so associated with uncircumcision that they are as good as saying, "This means that God has enabled the Uncircumcised to do repentance and have life!" In other words, "Wow! So its possible to obtain life, to join the covenant community without circumcision!!" This seems to me to be the argument that Paul spends so much time positing / defending, as well as the context of these verses.
3. I foresaw your objection that there is no comparable sending of the Messiah as prophet to the Gentiles. But might not your own apologetic, that the "Son of Man" refers not only to an individual, but to a community, have application here? The "body of the Messiah" having an almost organic unity with the Messiah within Paul’s epistles. Might Peter (just this once) be ahead of the game and foressing this "mystery now revealed"?? Just a thought…

P.s. I’m intrigued by your comment about Jesus return:

then he will be sent again to restore all things - that is, restore the kingdom to Israel (cf. 1:6).

When does this take place within your CoSM schema? 

Regards,
 John