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. 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.
It's the Jewish law in Torah that Paul wrote doesn't apply to gentiles. I don't know of a single Christian church that requires any of the extensive ritual law in Torah.
Even most Jews no longer practice the ritual law. Certainly not reform Judaism or conservative Judaism. I think it's basically only the Orthodox Jewish minority that keeps sabbath and kosher laws.
Torah is only the books of Moses, a fairly minor part of the OT. I never felt like all the extensive Hebrew history in the OT was very important or fundamental for the Christian liturgy. The wisdom literature and poetry in the OT is nice. I don't recall it ever being included as a key part of the Christian liturgy or sacrament. The OT is there for reference, and prophecy.
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.