The section ending Romans 9 and starting 10, Gal 3 on voiding and replacing the Promise , and Eph 3 on the shared benefits of all believers “through the Gospel” are definitive Biblical structure.
In Exodus 33:13, Moses wanted God to be gracious to him by teaching him to walk in His way that he and Israel might know Him, in 1 Kings 2:1-2, God taught how to walk in His way through His law, and in Matthew 7:23, Jesus said that he would tell those who are workers of lawlessness to depart from him because he never knew them, so knowing God and Jesus is the goal of the law, which is eternal life (John 17:3).
In Romans 9:30-10:4. they had a zeal for God, but it was not based on knowing Him, so they misunderstood the goal of the law by pursuing it as through righteousness were earned as the result of their works in order to establish their own instead of pursing the law as through righteousness were by faith in Christ, for knowing Christ is the goal of the law for righteousness for everyone who has faith. In Romans 10:5-10, it references Deuteronomy 30:11-20 as the word of faith that we proclaim in regard to saying that God's law is not too difficult for us to obey, that obedience to it brings life and a blessing, in regard to what we are agreeing to obey by confessing that Jesus is Lord, and in regard to the way to believe that God raise him from the dead.
If you want to see justification best, you would be in ch 3:21-31. But not much of that is Biblical structure saying how the Promise, Law and Gospel relate.
In Matthew 4:15-23, Jesus began his ministry with the Gospel message to repent for the Kingdom of God is at hand, which was a light to the Gentiles, and God's law was how his audience knew what sin is (Romans 3:20), so repenting from our disobedience to it is a central part of the Gospel of the Kingdom, which is in accordance with Jesus being sent in fulfillment of the promise to bless us by turning us from our wickedness (Acts 3:25-26), which is the Gospel of the Kingdom that was made known in advance to Abraham in accordance with the promise (Galatians 3:8), and which he spread to those in Haran in accordance with the promise (Genesis 12:1-5).
In Genesis 18:19, God knew Abraham that he would teach his children and those of his household to walk in His way by doing righteousness and justice that the Lord may bring to him all that He has promised. In Genesis 26:4-5, God will multiply Abraham's children as the stars in the heave, to his children He will give all of these lands, and through his children all of the nations of the earth will be blessed because he heard God's voice and guarded His charge, commandments, statutes, and laws. In Deuteronomy 30:16, if the children of Abraham will love God with all of their heart by walking in God's way in obedience to His commandments, statutes, and laws, then they will live and multiply, and God will bless them in the land that they go to posses, which is again the word of faith that we proclaim (Romans 10:5-8). So the promise was made to Abraham and brought about because he walked in God's way in obedience to His law, he taught his children and those of his household to do that in accordance with spreading the Gospel of the Kingdom, and because they did that.
In Psalms 119:1-3, God's law is how the children of Abraham know how to be blessed by walking in God's way, and in John 8:39, Jesus said that if they were children of Abraham, then they would be doing the same works as him, so the way that the children of Abraham are multiplied and are a blessing to the nations in accordance with inheriting the promise through faith is by turning the nations from their wickedness and teaching them to do the same works as Abraham by walking in God's way in obedience to His law in accordance with spreading the Gospel of the Kingdom.
3:
The above notes on Rom 9-10 don't appear to relate to the Promise and Law and Gospel elements that are in Galatians 3. But they do: they amount to mistaking the Law for a promise, pretty much removing what the Promise had said. Gal 3:17-18 repeat the problem clearly, with 2 verbs in v17 for the problem. "Someone" (guess whom?) has canceled a previous covenant and invalidated the promise. You might, borrowing on what Rom 9 said, put 'treated the previous covenant and promise as though canceled and invalidated.' Something has definitely been replaced! Not by God, of course, but in the mind of Judaism.
But v18 makes it clear that it can't be: the inheritance of being in Israel can't be based on law (this should sound much like Rom 9's 'sought to establish their own righteousness'), but was a promise. Just as Rom 9 said, one route cannot get to what God was offering, that route of works. Gal 3 says an inheritance based on the law is no longer based on a promise.
I won't take up the question of whether this meant the land of Israel, but there is no indication in Gal 3 that it does; only that there was something of huge value to the nations. It would be better to answer this in Eph 3, below.
(cont.)
Something that is inherited is not something that is earned as the result of our works, so while the promise is not earned as the result of our works, that does not mean that the content of the promise is not in regard to blessing the nations by turning them from their wickedness and teaching them to obey God's law in accordance with the Gospel of the Kingdom. In Galatians 3:16-19, it is just as true that the New Covenant does not nullify the promise of a covenant that has already been ratified, so it is also true that it does not nullify our need to obey God's law in connection with the promise, but rather the New Covenant still involves following God's law (Jeremiah 31:33). Moreover, in Galatians 3:26-29, every aspect of being children of God, through faith, in Christ, and children of Abraham and heirs to the promise is directly connected to walking in obedience to God's law. In 1 John 2:6, those who do not practice righteousness in obedience to God's law are not children of God, in Matthew 23:23, Jesus said that faith is one of the weightier matters of God's law, and in 1 John 2:6, those who are in Christ are obligated to walk in the same way he walked.
In Ephesians 3:6, the mystery is that the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel, so again it directly connects Gentiles inheriting the promise with being children of Abraham and spreading the Gospel of the Kingdom.