In Exodus 12:38, there was a mixed multitude that came up out of Egypt with them, so there were Gentiles at the foot of Sinai, and in John 8:33, Israel was inclusive of both the foreigner and the native born, so Israel is inclusive of everyone who is a follower of the God of Israel in obedience to His law. In Ephesians 2:12-19, Gentiles were once separated from Christ, alienated from Israel, strangers to the covenants of promise, having no hope, and without God in the world, but through faith in Christ all of that is no longer true in that Gentiles are no longer aliens or strangers, but are fellow citizens of Israel along with the saints in the household of God. In 1 Peter 2:9-10, Gentiles are included as part of God's chosen people, a holy nation, a royal priesthood, and a treasure of God's own possession, which are terms used to describe Israel (Deuteronomy 7:6), so Gentiles also have the delight of getting to follow the laws that God gave for how to fulfill those roles. For example, it would be contradictory for a Gentile to want to become part of a holy nation while not wanting to follow God's laws for how to live as part of a holy nation.
In Jeremiah 31:33, the New Covenant was only made with those house of Judah and the house of Israel, so it is only through faith in Christ that Gentiles are able to become joined to Israel and become partakers of the New Covenant. Furthermore, Jeremiah 31:33, the New Covenant involves God putting the Torah in our minds and writing it on our hearts, so if someone wants nothing to do with becoming joined to Israel through faith in Christ and with obeying the Torah, then they want nothing to do with the New Covenant.
Either Acts 15:19-21 contains an exhaustive list of all of the laws of the Torah that would ever be required of a mature Gentile believer or it does not, so it is contradictory for someone to treat it as being a non-exhaustive list by saying that there are obviously other laws that Gentiles should follow while also treating it as being an exhaustive list to limit which Gentiles should follow. For example, Gentiles are clearly expected to refrain from doing the things listed in 1 Corinthians 6:9-11, Galatians 5:19-21, and Titus 3:1-3, as well as obey the Ten Commandments and the greatest two commandments. Furthermore, if you agree that Gentiles should obey the greatest two commandments, then you should agree that Gentiles should obey the laws that hang on them, for example, if we love God and our neighbor, then we won't commit adultery, theft, murder, idolatry, kidnapping, rape, favoritism, and so forth for the rest of the Torah.
The Bible frequently uses parallel statements that are two ways of expressing the same thought, so Jesus was equating his commandments with those of the Father. Jesus was one with the Father, so he was not in disagreement with Him about which commandments we should follow and did not make any changes to them in violation of Deuteronomy 4:2. You are interpreting John 15:10 as if Jesus were hypocritically saying that we should only do as he said, but not as he did even though we are told to follow his example (1 Peter 2:21-22). They did not refer to it as "the Old law" at that time, so that is anachronistic.
I probably used to use those same verses to argue the same position, but my interpretation of those verses did not stand up to scrutiny. The Psalms express an extremely positive view of the Torah, such as with David repeatedly saying that he loved it and delighted in obeying it, so if we consider the Psalms to be Scripture and to therefore express a correct view of the Torah, then we will share it as Paul did (Roman 7:22), while anything less than the view that we ought to delight in obeying it is incompatible with the view that the Psalms are Scripture. Moreover, the NT authors considered the Psalms to be Scripture, so they should be interpreted as though they held the same view of the Torah that is expressed in the Psalms rather than as having a view of the Torah that is incompatible with what they considered to be Scripture. Instructions for how to testify about the nature of the God of Israel can't be abolished without first abolishing the God of Israel, so the reject of the Torah is the rejection of the God of Israel.
The Torah is God's word and Jesus is God's word made flesh, so the way to accept Jesus is by following his example of obedience to the Torah in accordance with Ezekiel 36:24-39 while the way to reject him is by refusing to obey the Torah.