doesn't say
promises, it says promise, singular. The promise he is talking about is the promise that Abraham would be "heir of the world", which was first made in
Gen. 12.
"
and the father of circumcision to those who not only are of the circumcision, but who also follow in the steps of the faith of our father Abraham which he had while uncircumcised. For the promise to Abraham or to his descendants that he would be heir of the world was not through the Law, but through the righteousness of faith." (
Rom 4:12-13 NASB)
As you said, Paul is chronicling the faith of Abraham here and it starts in
Gen. 12, when he first had faith (
Heb. 11). Did this faith justify him? Paul plainly says that this faithful acceptance was "through the righteousness of faith". So the answer is clearly "yes". Even if we ignore the overwhelming evidence I laid out on
Heb. 11 (which you have been doing), this alone should be enough to prove that in Paul's mind, Abraham accepted the "promise" in
Gen. 12 "through the righteousness of faith", and this plainly means he was justified.