In
Matthew 4:15-23, Jesus began his ministry with the Gospel 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 (
Romans 3:20), so repenting from our disobedience to it is a central part of the Gospel of the Kingdom. Jesus also set a sinless example for us to follow of how to walk in obedience to God's law and as his followers we are told to follow his example (
1 Peter 2:21-22) and that those who are in Christ are obligated to walk in the same way that he walked (
1 John 2:6). Jesus did not establish the New Covenant in order to nullify anything that he spent his ministry teaching or so that we could be free 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 God's law (
Jeremiah 31:33), so I have been speaking about how we should live under the New Covenant.
In
Colossians 2:16-23, they were keeping God's feasts in obedience to His commands in accordance with the example that Jesus set for us to follow, they were being judged 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 celebrating feasts.
Jews were given the role of being a light and a blessing to the nations by turning the nations from their wickedness and by teaching them to walk in God's way in obedience to His law in accordance with the promise and with spreading the Gospel of the Kingdom. In
1 Peter 1:16, we are told to be holy for God is holy, which is a quote from Leviticus where God was giving instructions for how to do that, which includes refraining from eating unclean animals (
Leviticus 11:44-45) and 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.
I don't see a reason to think that the Law of Christ is something other than or contrary to anything that Christ spent his ministry teaching.
Those verses say that cursed is everyone who does not continue everything written in the Book of the Law, so the position that we should continue to do everything written in it is the position that we are not under its curse (which is my position) while the position that we should not continue to do everything in it puts ourselves under its curse (which is your position). According to Deuteronomy 27-28, relying on the Book of the Law is the way to be blessed while lawlessness is the way to be cursed, so
Galatians 3:10 should not be interpreted as Paul quoting from that passage in order to support a point that is arguing the opposite of that passage, but rather the way to be cursed is by not relying on the Book of the Law, which is why everyone who relies on works of the law instead come under its curse.
In Titus 2:14, it doesn't say that Jesus gave himself to redeem us from God's law, but to redeem us from all lawlessness and to purify for himself a people of his own possession who are zealous for doing good works, so the way to believe in what Jesus spend his ministry teaching and in what he accomplished through the cross is by becoming zealous for doing good works in obedience to God's law (Acts 21:20) while the way to reject everything that he accomplished is by returning to the lawlessness that he gave himself to redeem us from. So the freedom that we have in Christ is not the freedom to be lawless, but the freedom from lawlessness.
The Gospel of the Kingdom is in accordance with Jesus being sent in fulfillment of the promise to bless us by turning us from our wickedness (Acts 3:25-28), which is the Gospel that was made known in advance to Abraham in accordance with the promise (Galatians 3:8), so you are interpreting that passage in a way that is contrary to the blessing given to Abraham that comes to Gentiles through Christ so that by faith we might receive the promise of the Spirit.
God is sovereign, so we are all under His law. God's law came with instructions for what to do when His children sinned, so it did not require us to have perfect obedience, and someone who continues to be a doer of God's law by repenting does not come under His curse. In Deuteronomy 11:26-32, the difference between being under God's blessing or his curse is not based on whether or not we have perfect obedience, but based on whether we choose to serve God or to chase after other gods. While all have sinned and fallen short of the glory of God, everyone being under God's curse does not reflect the reality of what is recorded about those who served God, just those who chased after other gods. Jesus redeemed us from the curse of lawlessness so that we could be free to enjoy the blessing of lawfulness. Sin is what is contrary to God's eternal character traits regardless of which covenant someone is under, but the New Covenant is still made with the same God with the same character and therefore the same instructions for how to be a doer of His character traits.