Its important that every scripture fits the "Historical Gospel" of Jesus Christ so that you have correct doctrine.
Romans 4:8 fits the Gospel just fine.
Jesus reconciles the world to God, 2 Corinthians 5:18, 19 and because of that God is at peace with the world, Colossians 1:20. But that does not mean that their will not be a judgment of believers and unbelievers when Christ returns.
Romans 4:8 is in the Bible, deal with it.
I love Romans 4:8! and it fits perfectly right where Paul wrote it (which is a quote from Psalm 32).
It fits perfectly with all the verses that surround it.
Hopefully, one day you will come to understand that once sins are forgiven, God doesn't change His mind.
That is the hope of the believer in Christ; in His faithfulness to not charge our sins against us.
Romans 4:8 is not about what God might or might not do, it is about what is ALREADY DONE!! if you truly believed that Jesus atoned for ALL the sins of the whole world, then they are all GONE...no where to be found...forgiven fully and completely and finally!
Abraham is a real person who exhibited real faith and received a real righteousness that was credited to his account. Through him, countless peoples have also received a real blessing of righteousness by faith; not Jews only, but also Gentiles. It was not by works, but by promise. The same promise that I, myself, through faith, am believing that my sins are fully, completely and finally forgiven for EVER.
If you want to believe in some kind of temporary forgiveness of sins, or the forgiveness of only some sins, or a god who changes it's mind or whatever you actually believe, then that's on you.
But we who understand what Paul is writing in Romans 4, will continue to glory in the promises of the unchanging God of Abraham, that we, through faith such as Abraham's, will continue to trust that our sins are removed from us forever.