Sincerity is no guarantee for Truth.
There are some who like to put themselves under the law for the feeling of self-righteousness…our righteousness was made unto us through Christ
The gospels (the law), was written for Israel …
Romans 1-8 is a doctrinal epistle written directly to us… the Church of God, and goes through what was made unto us by Jesus Christ.
You are quite right, but the law is eternal in that it is the blueprint followed for Creation.
There are unspoken laws: How our heart beats, the seasons, the instincts of the animals. Everything altogether is the eternal law.
The part that pertains to man is his moral failure. This chapter was written in stone for a future Jesus to come and receive all the blessings by never offending any part of Creation or the law----especially the part of being condemned if you are a sinner.
Jesus was a sinner in the eyes of God as part of the plan for man's imputed righteousness and saving. Like reading a book about mobsters, when we close the cover of that book and put it on the night stand we can sigh in relief that it sure isn't written about ourselves. A book on the error of our life can also be closed, as all that wrong never happened to us, but to Jesus when he took responsibility and credit for all of it as a hero.
It is said at the end of Romans 4 that Jesus was PERMITTED to rise from the grave because of our saving. Think about that: Because of our salvation Jesus was saved. It does follow that should anyone be able to fall away and lose his salvation then Jesus wouldn't be the perfect hero any longer and would be required to return to the grave and to hell. It is an exacting science that God follows: justice. But, since Scripture clearly states that Jesus is on his throne in heaven forever, that no one is capable of losing their salvation.
There are passages that are clumsily misinterpreted. In Hebrews the OPPORTUNITY for salvation is called the Tree of Life. The statement involves those being removed from that tree to make room for the gentiles, and even the gentiles upon unbelief will be removed from the Tree of Life. The key word in both incidences is UNBELIEF, or TRUST or VALUING the plan of the gospel. If anyone who valued their saving from a doomed state puts their trust in Jesus it is stated that Jesus will NEVER, NEVER, NEVER leave or forsake that person. It is stated also that nothing of any possible situation or thing cannot remove us from the grip God has on us through the plan of The Father: The gospel. That would certainly refer to our own sin as well.
The reason Jesus didn't need to die billions of deaths for billions of people is that all believers become one with him as his body.