Nice post.
Yes, I don't think the New Testament voids the prohibition against murder, theft, adultery in the OT. Those can be thought of divine eternal law.
It's reasonable to parse the law into "ritual purity" and "divine eternal" except insofar as the BIble does NOT make this distinction. Nowhere to my recollection does Jesus say "...Till heaven and earth pass, one jot or one tittle shall in no wise pass from the "ritual purity" laws, till all be fulfilled."
It is a nice exegesis to break the law up this way. And certainly it kind of feels like dispensationalism.
It really seems that it is yet one more way to square the circle of the Bible. Along with simply jettisoning those books one doesn't necessarily feel comfortable with (as you do with the OT) it really helps move God into a more ecumenical, universal God.
As opposed to the fierce partisan for a tiny uplands tribe in a desertified corner of the world.
The fact that Jesus' sermons and parables about proper moral justice and human relations echo the divine moral law in the OT means in theory, you don't have to turn the pages back to the OT to see those laws... those eternal moral laws are echoed in the moral teachings of Jesus -- they're in the NT, you don't have to flip the pages back to the OT to understand the eternal divine law.
Yes, Jesus seems to on the whole recast the laws in simplified forms without reliance on the ritual purity laws. Or at least the authors of the Gospels do.
This is the stuff I find valuable in the Bible. It is the good stuff. But it is hard to parse that out from the OT when even Jesus states: "...Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled."
It's the Jewish law in Torah that Paul wrote doesn't apply to gentiles.
Even THAT was a debate in the early Church. I believe you said elsewhere something I agree with: Paul is largely responsible for Christianity. (Apologies if you didn't say that, but it is something that makes a lot of sense) which really kind of is a "John Smith with the golden tablets" kind of moment. A way to see how the "sausage" of a new faith is created leveraging the tenants (loosely) of the old faith and upending it simultaneously.
But most Christians would still prefer the faith to be defined by Christ, not someone who never met him.
I think the reason the OT reads some differently from the NT is because the OT is based on a Mesopotamian cultural and religious motif. The NT was written by Hellenized Jews, and influenced by Greek philosophy and Greek Hellenized culture.
The reason it is important to keep the OT in mind when reading the NT or being a Christian is:
1. It is the "origin story" of the faith. Jesus relies on the older faith to build his newer church
2. It is as viable and valid a "biography" of God as anything else. It is presumably the SAME God as in the NT
3. It is disallowed per the Christian faith to simply jettison the OT (Marcionite Heresy)
4. It is an EXCELLENT x-ray of the "God-Concept" to show how God EVOLVES exactly as a human construction would be expected to. (Why would God suddenly become a lover of all people across the earth after being a partisan handing over towns to his chosen people to be slaughtered by them or commanding genocides through his prophet?)
The OT is where we first meet God. The NT is the next book in the series and the authors decided that they needed to "change up" the character to make him fit more current times.
We even see it today! God is constantly changing to meet our needs.
That's the whole point of keeping the OT in mind in these discussions.