Appeals to Matthew 6:16-18 need qualification. The Sermon on the Mount presents Jesus as the New Moses or New Lawgiver and Jesus qualifies the authority of the Law with His oft repeated magisterial phrase, "You have heard it was said, but I say unto you." Jesus champions exceptions to Sabbath rest by His Sabbath healings and by the permission He gives for His disciples to gather grain on the Sabbath. Then as the New Lawgiver, Jesus offers this principle to govern the Sabbath: "The Sabbath was made for people, not people for the Sabbath. Therefore the Son of Man is Lord even of the Sabbath (Mark 2:27-28)."
Jesus was born under the law, which means that if He had added to or subtracted from the Mosaic law, then he would have sinned (Deuteronomy 4:2) and disqualified himself from being our Messiah. However, when the Sermon on the Mount is correctly understood, Jesus did not give any brand new commandments. Whenever he quoted from Scripture, he preceded it by saying, "it is written", however, when he was quoting what the teachers of the law of his day were teaching, he preceded it by saying, "you have heard that it was said", so Jesus was not sinning by making changes to the law, but was correcting what was being wrongly taught about it. This would have sounded to the teachers of the law like he was abolishing the law, so he preceded it by saying that he came not to abolish the law, but to fulfill it, and the proceeded to fulfill the law six times by correctly teaching how to understand and obey it. For example:
Matthew 5:43 “You have heard that it was said, ‘Love your neighbor and hate your enemy.’
While the law does instruct us to love our neighbor (Leviticus 19:18), it does not say to hate your enemy, which was what was being wrongly taught about the law. So Jesus is like Moses in that he also taught how to live according to God's holiness, righteousness, and goodness in obedience to His law. If the way to act in line with God's character has changed, then God's character has changed, but God is eternal and does not change. The Sabbath was never meant to be used as an excuse to avoid doing the good of healing people, so Jesus did not break the Sabbath, but rather he likewise taught how to correctly obey it.
Finally, Jesus limits the duration of Sabbath laws:"The Law and the Prophets were in effect until John came (Luke 16:16)."
I'm not sure how you can interpret Luke 16:16 as Jesus saying that the Law and the Prophets are now void when you look at the context. In the second half of the verse that you cut off, Jesus talked about the good new of the kingdom of God being preached since John, which is to repent from our disobedience to the Mosaic law for the kingdom of God is at hand. In verse 17, Jesus affirmed the permanence of the law by saying that it is easier for heaven and earth to pass away than for one stroke of a letter in the Torah to become void. In verses 18 and beyond, Jesus spoke against adultery, while in verses 15 and before, Jesus spoke against coveting. According to Psalms 119:160, all of God's laws are eternal, and in Matthew 19:17, Jesus said that if you want to enter into life, then keep the commandments, so this does not sound at all to me like he was sinning by saying the eternal law of God was temporary.
Paul clarifies what this means by declaring: "Christ is the end of the Law for everyone who believes (Romans 10:4)." In other words, by His atoning death Christ brings the Law and its system of forgiveness to an end. But this does not mean that principles in the Law of Moses cannot be renewed for the Christian era (e. g. the Law's prohibition against homosexual sex acts.).
The Greek word "telos" can mean "end", but it is talk about the "end" as in the goal or purpose of the law, not its termination. The law is pointed at or directed toward Messiah and he is the goal or purpose of the law because the law is entirely about him and about how to grow in a relationship with him based on faith and love for righteous for all who believe. The way to act in line with God's holiness, righteousness, and goodness cannot come to an end unless God's holiness, righteousness, and goodness first comes to an end.
But it does mean that the 4th Commandment to honor the Sabbath can be replaced by Sunday worship in honor of "the Lord's Day," Easter Sunday. The Greek word for "the Lord's Day" is "kyriake" (see Revelation 1:10). A roughly contemporary Gospel, the Gospel of Peter, makes it clear that "kyriake" refers to Easter Sunday.
Jesus criticized the Pharisees for setting aside the commands of God in order to follow their own traditions, and that is precisely what is done when people set aside God's Sabbath to follow their tradition of worshipping on Sunday. The Day of the Lord is a Jewish eschatological phrase that refers to the end of days, so Revelation 1:10 is referring to the day that John was seeing in his vision, not to the day that he happen to have his vision. I do not see anywhere in the Gospel of Peter where it talks about Easter Sunday, but rather he rose on the Feast of Firstfruits and his resurrection was incorporated into that celebration with him being being the firstfruits of the dead.
That does not mean that Paul condemns the Jewish practice of continuing to honor the Sabbath: "One person esteems one day above another. Another person esteems every day the same. Let every one be fully persuaded in his own mind (Romans 14:5)." But Paul is indignant at Jewish Christians who criticize Gentile Christians for making Sunday their holy day: "Let no one condemn you over... festivals and new moons and Sabbaths (Colossians 2:16)."
We must obey God rather than man, so it is important not to take something that was against obeying man as being against obeying God. The subject of the Romans 14 is stated in the first verse, namely that it is regard to disputes of opinion, not in regard to whether we should obey the commands of the God that we follow. Paul was certainly not suggesting that it was ok to commit murder, theft, adultery, or to sin in disobedience to any of God's other commands just as long as you were convinced in your own mind that it was ok. In Romans 14:5-6, it is talking about those eating or refrain from eating, so it is talking about those who esteem certain days for fasting. The only day that God commanded fasting is on the Day of Atonement, but as a matter of opinion, it had become a common practice to fast twice a week to commemorate certain events (Luke 18:12). Those who esteemed those days for fasting were judging those who did and were in turn being resented, so it was this sort of judging each other over opinions that Paul was seeking to quell. We are not to keep the Sabbath because man esteemed it, but because God esteemed it, blessed it, made it holy, commanded it to be kept, and because we should not profane what is holy to God. So whether someone fasts on other days is a disputable matter of opinion, but whether someone fasts on the Day of Atonement is a matter of obedience to God.
Likewise, Colossians 2:16 had nothing to do with Jewish Christians criticizing Gentiles for making the Sabbath their holy day.
Colossians 2:8 See to it that no one takes you captive by philosophy and empty deceit, according to human tradition, according to the elemental spirits of the world, and not according to Christ.
Paul would never have referred to those teaching obedience to the holy, righteous, and good commands of God as teaching philosophy and empty deceit according to human tradition. It is absurd to say that the commands of God are against Christ because Christ is God and he lived in perfect obedience to them. Paul went into more details about what these elemental spirits of the world are later in the chapter:
Colossians 2:20-23 If with Christ you died to the elemental spirits of the world, why, as if you were still alive in the world, do you submit to regulations— 21 “Do not handle, Do not taste, Do not touch” 22 (referring to things that all perish as they are used)—according to human precepts and teachings? 23 These have indeed an appearance of wisdom in promoting self-made religion and asceticism and severity to the body, but they are of no value in stopping the indulgence of the flesh.
So the Colossians had been keeping God's Sabbath, Festivals, and New Moon in obedience to God and were being judged by those teaching human precepts and traditions, self-made religion, asceticism, and severity to the body. Paul was writing to encourage them not to let any man keep them from obeying God, which again goes back to the theme that we must obey God rather than man.
