I must make my calling and election sure:
If I fall away, it was because I was not chosen.
So then, from your own personal perspective, YOU do not know whether you are elected or not until "the end", because you might fall away.
So from a human perspective, "pre-destination" is just an intellectual debate.
This is why I prefer to talk about God pre-destining GROUPS. The "elect" might be pre-destined, but you do not KNOW personally that you are of the elect, because as you acknowledge, you have to make your calling and election sure.
Paul is speaking about the elect Jews in these passages, not national Israel. The Bible does not teach dispensationalism and it does not teach salvation by any other way than grace through faith. Abraham was justified before God by faith...so are the elect Jews...so are the elect Gentiles.
Not so. Paul has already identified the believing Jews in his argument...
"What then? Israel failed to obtain what it was seeking. The elect obtained it, but the rest were hardened..." (11:7)
He then goes on to ask: "So I ask, did they stumble in order that they might fall?" (11:11)
He is obviously talking about non-believing Israel here. THEY were the ones that stumbled. Then he goes on to say:
"By no means! Rather through their trespass salvation has come to the Gentiles, so as to make Israel jealous. Now if their trespass means riches for the world, and if their failure means riches for the Gentiles, how much more will their full inclusion mean!" (11:11,12)
Make who jealous? ISRAEL... physical Israel. Why would spiritual Israel be jealous?
If THEIR trespass... whose trespass? PHYSICAL ISRAEL... means riches for the world... and their failure [physical Israel's failure] means riches for the Gentiles, how much more will their [physical Israel] full inclusion mean?
Paul is talking to the nations about his physical brothers the Jews.
"Now I am speaking
to you Gentiles. Inasmuch then as I am an apostle to the Gentiles, I magnify my ministry in order somehow to make
my fellow Jews jealous, and thus save some of them. For if
their rejection means the reconciliation of the world, what will their acceptance mean but life from the dead?"
"For if THEIR REJECTION [that is, the Jews' rejection] means the reconciliation of the world, what will THEIR ACCEPTANCE [the Jews' acceptance] mean but life from the dead?"
You're right that there is only one people of God... but you are also missing the fact that Paul argues, and lays out the plan, for how God intends to graft back in PHYSICAL Israel.
"And even they, if they do not continue in their unbelief, will be grafted in,
for God has the power to graft them in again. For if you were cut from what is by nature a wild olive tree, and grafted, contrary to nature, into a cultivated olive tree,
how much more will these, the natural branches, be grafted back into their own olive tree." (11:24)
For someone who believes in the power of God and election, it seems you pick and choose which verses you actually HEAR.
Paul is talking about JEWISH unbelievers. They were "natural branches", and therefore "much more" able to be grafted back INTO THEIR OWN OLIVE TREE!
This is why Paul says "a partial hardening has come upon Israel,
until the fullness of the Gentiles has come in..."
Yes, you're right that God hardened Israel, but notice that word... UNTIL.
It is a hardening of LIMITED DURATION.
When Paul said, "all Israel would be saved"... if he meant simply that all of God's people are now "Israel", then he wouldn't have talked about them being grafted in again, immediately before
Paul is making the case that not only CAN they be grafted back in, but they WILL be.
Indeed, notice also what Paul says immediately AFTER his famous "all Israel will be saved" statement...
"As regards the gospel, they are enemies of God for your sake. But as regards election, they are beloved for the sake of their forefathers. For the gifts and the calling of God are irrevocable." (11:28)
So while I agree with you: Paul IS making a case that Israel is not just the physical nation of Israel... he is also making the case that the physical nation of Israel will eventually be grafted back into their own olive tree, "that he may have mercy on all." (11:32)
Remember... "a partial hardening has come upon Israel,
until the fullness of the Gentiles has come in..."
UNTIL.
The hardening of Israel was to be of limited duration. And if God did the hardening, then He will do the softening again.
This is the real "mystery" that Paul revealed, but that even Gentile Christians like yourself find hard to grasp... perhaps because we, too, can be blinded.