ALL in context of romans 11 is Israel.
Paul is saying, just like the OT prophets predicted there will be a time to come. When the time of the gentile is complete. That Israel as a nation will repent.
When ALL Israel is used. Gentile believers are not included in that context.
Especially with regard to the part of your observations I made
bold above. You should
read Romans 11 first.
What does Romans chapter 11 mean?
This passage concludes a significant section of Paul's letter, contained in Romans 9—11. These three chapters ask and answer the question, "What about Israel?" This is an objection Paul's opponents often asked. If Israel is God's chosen people and they have rejected faith in Christ as the way of salvation, what will happen to them?
Paul has acknowledged that Israel has, for the most part, rejected faith in Christ. He begins this chapter by asking if that means that God has rejected Israel. His response is another resounding "no." After all, Paul himself is an Israelite who has come to faith in Christ and has been saved, showing that this is possible for all Jewish people. Paul refers to the smaller subset of Jewish people who have turned to Christ as a remnant, comparing them to the remnant of those in Israel who had not bowed to Baal in Elijah's day. By His grace (Romans 9:6–8), God has set aside this remnant of Jewish Christians as true Israel (Romans 11:1–5).
Paul also makes a clear point about any attempt to mix salvation by grace with salvation based on works. In short, they are totally incompatible. If something is truly by "grace," it cannot be in any way based on works, and vice versa (Romans 11:6).
What about the rest of Israel, though? What of those who refused to believe in Christ as the Messiah? Paul's startling revelation is that God has hardened their hearts in their initial unbelief. He has caused them to trip over the stumbling block of Jesus, but not permanently. Their hardening is only for a time (Romans 11:7–10).
One reason for Israel's unbelief, Paul writes, is to make room on the main body—referred to as "the root"— of God's tree. This open space is intended for the non-Jews in the world. These Gentiles who are coming to God through faith in Christ are like the branches of a wild olive tree that have been grafted onto the trunk of a cultivated plant. The old branches, unbelieving Jews, have been broken off for a time to make this possible (Romans 11:11–16).
Paul warns the Gentile Christians not to be arrogant toward these unbelieving Jews, however. The time is coming, after the right amount of the Gentiles have believed in Christ, when God will remove the hardening from the unbelieving Jews. They will turn to faith in Christ and, as a people, be grafted back onto God's symbolic olive tree, from which they had previously been pruned. God is not done with Israel (Romans 11:17–24).
In spiritual terms, the Israelites may be enemies of the gospel of faith in Jesus Christ, for now. They were certainly the spiritual enemies of Paul during his lifetime. And yet, the Jewish people of Israel remain deeply loved by God because of the promises He made to the patriarchs. God never breaks His promises. His gifts and His calling on Israel can't be taken back. God will use His grace and mercy toward the Gentile Christians to make Israel jealous. He will use these events to bring her back to Himself as a nation, in the form of those individual Jews who eventually trust in Christ at some future time (Romans 11:25–32).
Paul concludes this section with what has become a beloved poem, like a hymn, about the vast un-knowable-ness and independence of our merciful God (Romans 11:33–36).
