Did you notice in your posting from Galatians where Paul states: “This is what I mean: the law, which came 430 years afterward [after Abraham]”? Paul makes it clear here that he is talking about the Mosaic Law, not the eternal moral law of God. Both here and in Romans Paul is refuting the Judaizers who insist that believers must still be circumcised and follow the Mosaic Law, and that is all that he is saying.
If God’s Law that He handed down at Mt. Sinai could not save, then what law does?
“Abraham believed God and it was accounted to him as righteousness.”
Sounds like faith alone to me, and that’s all the way back in Genesis too.