I agree, and while I did not read your prior post, I would strongly agree that Romans 3 does indeed "foreshadow" Romans 9 in its treatment of how the nation of Israel has "failed".
Again, I agree. Paul is indeed making a "national" argument about Israel in Romans 9. And in so doing, and as you say, we should not imagine that Paul thinks that each and every Jew will be lost.
I totally agree. But, as I think you will agree it gets a bit tricky at the end of chapter 11 where Paul writes about "all Israel" being saved.
I am convinced that, just as in Galatians, Paul uses the term "Israel" to refer to the church.
This is where overly-simplistic analyses fail - the kind that insist that the term "Israel" must always denote the nation of Israel. This is clearly not always the case - it can be easily shown that, at times, Paul uses the term "Israel" to refer to the Jew + Gentile church.
Amen to all you said here. The only point I will add is that this trickiness at the end of chap 11 is only that we need to see Paul is saying "all Israel" in the sense of what he said here: Romans 9:6 ¶Not as though the word of God hath taken none effect. For
they are not all Israel, which are of Israel:
And the next few verses theren in chap 9 tie in to show an Israelite is who God decrees an Israelite at any given time from among who he wants when he chooses to do so.
Galatians 3:8 And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed.
9 So then they which be of faith are blessed with faithful Abraham.
Galatians 3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:
14 That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
15 Brethren, I speak after the manner of men; Though it be but a man's covenant, yet if it be confirmed, no man disannulleth, or addeth thereto.
16 Now to Abraham and his seed were the promises made.
He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.
If our sire of life (our father who gives us life) is a life giving spirit we in a spiritual way
become whatever he is. And he is an Israelite and a Jew. But showing that fleshly designation does not matter it becomes as though we have no nationality at all in Christ. He is Israel who prevails with God by virtue of having kept that Law and in whom we now prevail with God by virtue of his ransom and priestly intercession for us. That is the Israel of God.
Galatians 3:22 But the scripture hath concluded all under sin, that the promise by faith of Jesus Christ might be given to them that believe.
23 But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed.
24 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
25 But after that faith is come, we are no longer under a schoolmaster.
26 For
ye are all the children of God by faith in Christ Jesus.
27 For as many of you as have been baptized into Christ have put on Christ.
28
There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
29 And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.
I showed you the progression of this theme in my earlier posts on Romans chapter two and three. This theme is upheld in everything Paul says.