I hope these will give people help in thinking through these issues. My last word on this for now comes from Romans 9. Romans 6-8 is a great exposition of the effects of the gospel (6), the need for the gospel (7), and the benefits of the gospel (8). Someone might see Paul flattening out the distinction between Jews and Gentiles so much that they might wonder if he has any special place in his heart for ethnic Israel at all. I think he addresses that in Romans 9.1-5, and what he does is appeal to past history, not future.
Then he says in Rom 9.6, “But it is not as though the word of God has failed”. In other words, it looks like God made promises to ethnic Israel that have failed to come to pass. But it only looks like that on the surface. And notice what he does not say. He does not say “it hasn’t failed, because one day Israel will get the land of Canaan as promised” (or you can fill in the blanks of supposed promises to ethnic Israel).
Instead he says “for not all who are descended from Israel belong to Israel. And not all are children of Abraham because they are his offspring, but ‘through Isaac shall your offspring be named.’ This means that it is not the children of the flesh who are the children of God, but the children of the promise who are counted as offspring.” Paul is clearly using the words “Israel” and “offspring” in different ways. Ethnic Jews are not the children of God; spiritual children of promise are. God did not mainly make promises to ethnic Israel, or else God’s word has failed. The point of the OT was not for us to see God making promises to ethnic Israel, but to see God making promises to spiritual Israel (I actually prefer the language of “true Israel” vs. “spiritual Israel”; and I would say, True Israel is first of all Jesus, then secondarily those who are united to Him by faith; but I am happy to simply consider True Israel the Elect, i.e. the Church).