We become one new man where there is neither Jew or Gentile..........this says nothing of Gentiles keeping the law and in fact Galatians admonishes against it
One new man that should walk in God's way, not reject it. Jesus spent his ministry teaching his followers to obey God's law by word and by example and while Gentiles do not need to become Jews in order to become his follower, Gentiles can't follow him by refusing to follow what he taught.
1 Peter is written to the believing remnant of Israel.......we are not included as a chosen people, a holy nation, a priesthood
In 1 Peter 2:9-10, it is clearly speaking about Gentiles being included. The God of Israel has given instructions for how to know, love, glorify, believe in, and testify about Him by walking in His way, so those who want to do those things should follow His instructions for how to do them regardless of whether they are a Jew or a Gentile.
where does Paul say we partake of the new covenant
1 Corinthians 11:25
[Deu 5:2 KJV] 2 The LORD our God made a covenant with us in Horeb.
God made covenant with Israel only which included the sabbath
Israel was given the role of being a light and a blessing to the nations (Deuteronomy 4:5-8). Again, in Ephesians 2:12-19, Gentiles were at one time separated from Christ, alienated from Israel and the covenants of promise, but through faith in Christ all of that is no longer true in that Gentiles are no longer strangers or aliens, but are fellow citizens of Israel along with the household of God.
[Act 18:4 KJV] 4 And he reasoned in the synagogue every sabbath, and persuaded the Jews and the Greeks.
Paul preached Christ in the synagogue
Indeed, Paul was continuing to keep the Sabbath holy in obedience to God in accordance with the example that Jesus set for us to follow and while he was doing that he was preaching Christ.
Israel only will get the new covenant and a new heart to keep the law
In Acts 15:6-7 they said that Gentiles had heard and received the Gospel message, namely in Matthew 4:15-23, Jesus began his ministry with the the message to repent for the Kingdom of God is at hand, which was a light to the Gentiles, and God's law was how his audience knew what sin is, so Gentiles were repenting and living in obedience to God's law in accordance with the Gospel of the Kingdom. Likewise, in Acts 15:8-9, Gentiles had received the Spirit and God had cleansed their hearts, which is in accordance with the Spirit leading us to obey God's law (Ezekiel 36:26-27). In Acts 15:10-18, they quoted prophecies about about the inclusion of Gentiles into the restoration of Israel.
Again, Ephesians 2:12-19.