“Thus, the Church IS the Jewish remnant, with Gentiles grafted in to its members.”
You were doing great up until that point.
I know - it doesn’t always make sense - I just follow the word:
If some of the branches have been broken off, and you, though a wild olive shoot, have been grafted in among the others and now share in the nourishing sap from the olive root, do not boast over those branches. If you do, consider this: You do not support the root, but the root supports you. You will say then, “Branches were broken off so that I could be grafted in.” Granted. But they were broken off because of unbelief, and you stand by faith. (from Romans 11)