The goal of God's law is to graciously teach us how to know Him by embodying His likeness through being a doer of His character traits, so His character traits are the weightier matter of His law.
Everything in God's law is either in regard to how to love God or our neighbor, which is why Jesus said that those are the greatest two commandments and that all of the other commandments hang on them, so the position that we should obey the greatest two commandments is also the position that we should obey all of the commandments that hang on them. The way to love God is by embodying His likeness through being a doer of His character traits, such as the way to love justice is by being a doer of justice, the way to love holiness is by being a doer of His instructions for how to be holy as He is holy, and so forth. In other words, the goal of God's law is to graciously teach us how to love different aspects of His character traits, which is why the Bible repeatedly states that the way to love God is by obeying His commandments. The only way that we should cease to follow God's instructions for how to be holy as He is holy would be if God were to cease to be holy and if someone refuses to follow those instructions, then holiness is an aspect of God's character that they should not love.
God's righteousness is eternal (Psalms 119:142), therefore any instructions that He has ever given for how to be a doer of His righteousness are also eternally valid (Psalms 119:160), and if the way to be a doer of God's righteousness were temporary, then God's righteousness would also be temporary. God's way is the way to know Him and Jesus by embodying His likeness through being a doer of His character traits, which is the narrow way to eternal life (John 17:3). In Matthew 7:23, Jesus said that he would tell those who are workers of lawlessness to depart from him because he never knew them, so the law points us to Christ because it was graciously given in order to teach us how to know Him and we should live in a way that points to Christ by follow his example of obedience to it rather than a way that points away from him.
That verse could not be referring to a change of the law in regard to its content, such as with it becoming righteous to commit murder or sinful to do charity, but rather the context is speaking about a change in the priesthood, which would regard a change of the law in regard to its administration. A priesthood led by God's Word made flesh does not involve a departure from following God's Word.
God's law is am important foreshadow that testifies about the good things that are to come, so we should live in a way that testifies about the good things that are to come by following Christ example of obedience to it rather than a way that bears false witness against the good things that to come.
Ephesians 2:15 could not be referring to any of God's laws because all of God's laws are eternal. God did not make any mistakes when He gave His law, so He had no need to abolish His eternal character traits or any of His eternal instructions for how to be a doer of His character traits. God did not give any laws for the purpose of creating a dividing wall of hostility, but rather His law instructs to love our neighbors as ourselves. In Ephesians 2:10-15, we are new creations in Christ to do good works, so it would make any sense to think that Christ abolished his instructions for how to do good works, and indeed, the Greek word "dogma" is never used by the Bible to refer to the Law of God.
In Ephesians 2:12-19, Gentiles were at one time separated from Christ, alienated from Israel and strangers to the covenants of promise, without God and hope in their world, which is all in accordance with Gentiles at one time not being doers of the Law of God, 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 saints in the household of God, which is all in accordance with Gentiles becoming doers of the Law of God.
The purpose of God's law is to teach us how to have an intimate relationship with him by walking in His way, which is something that we need to keep on fulfilling.
Jesus and the Apostles quoted from the OT hundreds of times in order to support what they were saying, so it doesn't work to interpret them in a way that turns them against following what they considered to be an authoritative source. For example, Jesus quoted three times from Deuteronomy in order to defeat the temptations of Satan, which included saying that man shall not live by bread alone but by every word that comes from the mouth of God, so he affirmed God as being an authoritative source. In Deuteronomy 12:32, it is a sin to add to or subtract from God's law, so Jesus and the Apostles did not do that. In Deuteronomy 13, the way that God instructed to determine that someone is a false prophet who is not speaking for him is if they speak against obeying His law, so Jesus and the Apostles did not do that. It does work to interpret Jesus as speaking against obeying what God spoke in Deuteronomy 14 or to interpret the Apostles as speaking against following over 99% of what Christ taught.
Paul described the law that we are not under as being a law where sin had dominion over us, which does not describe the Law of God, but rather that is the role of the law of sin. In Romans 6:15, being under grace does not mean that we are permitted to sin, and in Romans 3:20, it is by the Law of God that we have knowledge of what sin is, so we are still under it.
In Colossians 2:16-23, the Colossians were keeping God's feasts in obedience to His commands, they were being judged for doing that by pagans who were promoting human teachings and precepts, self-made religion, asceticism, and severity to the body, and Paul was encouraging them not to let anyone prevent them from obeying God. Those promoting asceticism and severity to the body would be judging people for celebrating feasts, not for refraining from doing that.
Christ was not in disagreement with what God commanded.
Changing the medium upon which God's law is written from on stone to on our hearts does not change the content of what it instructs. For example, the command to honor our parents written on stone has the same content as the command to honor our parents written on our hearts. God has not commanded anything that wasn't in perfect accordance with living by the Spirit, which is why Paul contrasted those who walk in the Spirit with those who have minds set on the flesh who are enemies of God who refuse to submit to the Law of God (Romans 8:4-7). The character traits of God that the Law of God was graciously given in order to teach us how to embody that are the moral will of God are the fruits of the Spirit, which is why the Spirit has the role of leading us to obey it (Ezekiel 36:26-27).
God's character traits of eternal, so any instructions that God has ever given for how to be a doer of them are eternally and cumulatively valid regardless of which covenant someone is under, if any. While God can progressively reveal more instructions about how to be a doer of His character traits, those instructions will always be in accordance with what He has previously revealed. The Mosaic Covenant is eternal (Exodus 31:14-17, Leviticus 24:8), so the only way that it can be replaced by the New Covenant is if it cumulative with it. One thing can only make another thing obsolete to the extent that it has cumulative functionality, so a computer makes a typewriter obsolete but does not make a plow obsolete, which means that if the New Covenant involved doing something different that was not cumulative with the Mosaic Covenant, then it could not make it obsolete. So the New Covenant still involves following the Law of God (Hebrews 8:10) plus it is cumulatively based on better promises and has a superior mediator (Hebrews 8:6).
Jesus spent his ministry teaching his followers to obey the Law of God by word and by example and the reason why he established the New Covenant was not in order to nullify anything that he spent his ministry teaching or so that we could continue to have the same lawlessness that caused the New Covenant to be needed in the first place, but rather the New Covenant still involves following the Law of God (Jeremiah 31:33).