I am not sure how you can say this given the introduction:
1I am telling the truth in Christ, I am not lying, my conscience testifies with me in the Holy Spirit, 2that I have great sorrow and unceasing grief in my heart. 3For I could wish that I myself were accursed, separated from Christ for the sake of my brethren, my kinsmen according to the flesh, 4who are Israelites, to whom belongs the adoption as sons, and the glory and the covenants and the giving of the Law and the temple service and the promises, 5whose are the fathers, and from whom is the Christ according to the flesh, who is over all, God blessed forever. Amen.
6But it is not as though the word of God has failed.
While Paul does not directly say "here in this chapter, I will explain that God has indeed been faithful to His promises", I think that the above forces us to infer this. Why? Israel is presently in a bad state and yet she was given all the covenant promises. That is what verse 1 - 5 tell us. They are about the state of Israel to whom so many promises were made -adoption as sons, glory. In fact Paul explicitly identifies promises:
4who are Israelites, to whom belongs the adoption as sons, and the glory and the covenants and the giving of the Law and the temple service and the promises,
Give the sad state of Israel, and these promises that God made to her, what promises do you think are on Paul's mind when he writes this?:
6But it is not as though the word of God has failed.
Are you going to deny that the "word of God" is not a way of saying "the promises God has made". When I say "I keep my word", that is equivalent to "I keep my promises".
How can Paul not be saying that God has kept His promises to Israel and I am about to explain why?
Again, you ignore the context.
Paul throughout Romans is using diatribes to teach both the Jews (who would be extremely familiar with Diatribes) and the gentile (who by chp. 9 would now be catching on to Paul’s teaching method).
We were in agreement that for the most part Chp. 9-11 was especially written for the gentile, so what did Paul get across to the Gentiles in 9-11 using many diatribes?
As I stated and can show with examples in Romans the diatribe question will first be support by the logic for a positive answer with the negative logic presented afterwards (there can be a “No” right after the question sometimes).
Can we agree “14 What then shall we say? Is God unjust?” is a diatribe question with “not at all” being given afterwards?
If verse 14 is a diatribe question you should fine (being consistent with all of Romans) logical support before and/or after the question for a “yes” answer which in the case would be: “God has been unjust in the way he has treated the Gentiles as compared to the Jews”.
What shows God favoring the Jews over the gentile? How about : I speak the truth in Christ—I am not lying, my conscience confirms it through the Holy Spirit— 2 I have great sorrow and unceasing anguish in my heart. 3 For I could wish that I myself were cursed and cut off from Christ for the sake of my people, those of my own race, 4 the people of Israel. Theirs is the adoption to sonship; theirs the divine glory, the covenants, the receiving of the law, the temple worship and the promises. 5 Theirs are the patriarchs, and from them is traced the human ancestry of the Messiah, who is God over all, forever praised! Amen.
Paul says he would give up his own salvation for the Jews, but he did not say that about the gentiles, so is even Paul showing favoritism toward the Jews with verse 2-3?
Paul lists out the promises give the Jews and not the gentiles so is the not showing God’s favoritism toward the Jews?
Paul says: “It is not as though God’s word had failed”, that word went to the Jews and not the gentiles, so is God showing favoritism toward the Jews?
Paul goes on in verse 7-13 showing God to be “unjustly” favoring the Jewish descendants of Abraham, so it seems God is being “unjust”, but that is what Paul and others do when using the diatribe teaching method.