There is no such thing as Jew or Greek anymore. All who believe and follow God's Word are one in Christ.
We agree we are one in Christ. An I would agree we are heirs of the promises to Abraham.
Gal 3:27 For as many of you as were baptized into Christ have put on Christ.
Gal 3:28 There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus.
People of course continued to be male and female, Jew or Greek, etc. But they were still one in Christ.
And if you want to claim that Jewish believers no longer needed to keep the whole law, you can make that argument. But we know they did continue to keep the whole law. And we know gentiles were not required to do so. The issue of whether the Jewish believers would stop keeping the whole law was not addressed, because they intended to do so.
And this makes sense, because as we see in Acts 15 and 21 they had a different context to work in. Jews would get no traction at all preaching to other Jews that Jesus was the messiah, and the fulfillment of all the prophecies if they were not themselves keeping the law. They kept the law with Jesus as the fulfillment. This is still an approach messianic Jews use today to reach fellow Jews.
But they still were one body with the Gentiles who were not required to be circumcised and keep the whole law of Moses.
Gentiles are under moral law. They are not under every provision of the mosaic law. The Acts council clearly rejected that the gentiles had to be circumcised and keep the wholelaw of Moses.
But that is why I have asked what is "moral" law.
Circumcsion was required under the old covenant for descendants of Abraham, including Israel.
Physical circumcision was not required for Gentiles under the new covenant.
Spiritual circumcision, putting off the sinful nature, is required for both.
So here we have an example of a prior requirement of the covenant with Israel (and not directly related to sacrifices), that is no longer required for gentiles. So to say that everything required for Israel under the old covenant is now required for gentiles doesn't make sense.
The debate over the Sabbath is whether it is moral or ceremonial law. We can get to that shortly.