Again, if you understand what Paul is saying, He is saying that God's choosing of the nation of Israel was a calling. And the calling is irrevocable. They would always be Israel, the chosen people of God. It doesn't speak to the state of the people, other then they are chosen of God from all the other nations out there. There is no assumed "to salvation" anywhere. Just that God has called them to be separate from all the other nations. And that calling is irrevocable. It doesn't speak to consequence, or, again, the state of the people, as to saved or unsaved, believer or unbeliever. It is a corporal calling. You forget Moses' song, which God said was very important. It ends with the salvation of Israel. It ends withThe gifts of God are irrevocable not the designation of a race-nation. We know this from the final curse declared on Israel in Acts 3 if they did not recognize the new Moses.
I cannot write out 150 pages so please see my book and report after that. The Covenant Revolt. At Amazon.
"Rejoice, you nations, with His people;
For He will avenge the blood of His servants,
And will return vengeance on His adversaries,
And will atone for His land and His people.”"
Why did Moses have a song?
"16 The Lord said to Moses, “Behold, you are about to [h]lie down with your fathers; and this people will arise and play the prostitute with the foreign gods of the land into the midst of which they are going, and they will abandon Me and break My covenant which I have made with them. 17 Then My anger will be kindled against them on that day, and I will abandon them and hide My face from them, and they will be consumed, and many evils and troubles will find them; so they will say on that day, ‘Is it not because our God is not among us that these evils have found us?’ 18 But I will assuredly hide My face on that day because of all the evil that they will have done, for they will have turned away to other gods.
19 “Now then, write this song for yourselves, and teach it to the sons of Israel; put it [i]on their lips, so that this song may be a witness for Me against the sons of Israel. 20 For when I bring them into the land flowing with milk and honey, which I swore to their fathers, and they eat and are satisfied and become [j]prosperous, then they will turn to other gods and serve them, and spurn Me and break My covenant. 21 Then it will come about, when many evils and troubles find them, that this song will testify before them as a witness (for it shall not be forgotten from the mouth of their [k]descendants); for I know their inclination which they are [l]developing today, before I bring them into the land which I swore.”"
However, what did God say previously?
"30 “So it will be when all of these things have come upon you, the blessing and the curse which I have placed before you, and you [a]call them to mind in all the nations where the Lord your God has scattered you, 2 and you return to the Lord your God and [b]obey Him with all your heart and soul in accordance with everything that I am commanding you today, you and your sons, 3 then the Lord your God will restore [c]you from captivity, and have compassion on you, and will gather you again from all the peoples where the Lord your God has scattered you. 4 If any of your scattered countrymen are at the [d]ends of the earth, from there the Lord your God will gather you, and from there He will [e]bring you back. 5 The Lord your God will bring you into the land which your fathers possessed, and you shall possess it; and He will be good to you and make you more numerous than your fathers."
"6 “Moreover, the Lord your God will circumcise your heart and the hearts of your [f]descendants, to love the Lord your God with all your heart and all your soul, so that you may live. 7 And the Lord your God will [g]inflict all these curses on your enemies and on those who hate you, who persecuted you. 8 And you will again [h]obey the Lord, and [i]follow all His commandments which I am commanding you today. 9 Then the Lord your God will prosper you [j]abundantly in every work of your hand, in the [k]children of your womb, the [l]offspring of your cattle, and in the [m]produce of your ground, for the Lord will again rejoice over you for good, just as He rejoiced over your fathers; 10 [n]if you [o]obey the Lord your God, to keep His commandments and His statutes which are written in this Book of the Law, [p]if you turn to the Lord your God with all your heart and soul."
All of this is deep, and complicated. As Paul said in answer to His question "Has God then rejected Israel?" Paul says no, may it never be. And this under the inspiration of God. He is also the one who said that it is because the calling is irrevocable.
The church has an unfortunate history of deep antisemitism and hatred of the Jews. They have cause and reason, but it never died. (The heavy persecution of the Christians in the 1st and 2nd centuries is due to the Jews...so... reasons.) The Jews refused to tell Rome that Christianity is a branch of Judaism, in which it would have been recognized by Rome, and the exercise of that faith would be permitted. Judaism was the only other faith that Rome allowed outside of the worship of the Roman pantheon of gods, and the worship of the Emperor/Caesar.
Luther had a soft approach because he sought, through his congenial approach, to convert the Jews to Christianity. He had nothing good to say about Jews in Judaism. Nothing good at all. He had no tolerance, as they came to him at the diet, and he did not show them any tolerance at that time. Why? They weren't there to convert, but to get Luther to converse with them. Since it wasn't for conversion, there was no tolerance shown.