"done away with" is a strawman. If we quote Christ he came to fulfill, he did not come to abolish. The question is, what does a fulfilled law look like?
Jesus did not invent the concept of fulfilling the law, so we should seek to understand what it means to fulfill the law in the content of Judaism before Jesus said that he came to fulfill it in the way that his audience would have understood it. There is much discussion in the Talmud about how to fulfill the law in the sense of how to correctly meet our obligation to it. "To fulfill the law' mean "to cause God's will (as made known in the law) to be obeyed as it should be" (NAS Greek Lexicon: pleroo), so after Jesus said that he came to fulfill the law he then proceeded to fulfill it throughout the rest of the chapter by correcting what the people had heard being taught and by teaching how to correctly obey it as should be. According to Galatians 5:14, loving our neighbor fulfills the entire law, so again in regard to correctly obeying it, moreover, it refers to something that countless people of have done and should continue to do in perpetuity, not to something unique that only Jesus did. In Galatians 6:2, bearing one another's burdens fulfills the Law of Christ, so we should interpret that in the same way as we interpret fulfilling the Law of Moses.
Is circumcision fulfilled? Is the sacrifice fulfilled? They are not "done away with" but under Christ, our instruction is not dependent upon the legal code, but on deeper values. is do not murder, lie, steal fulfilled? These are moral thresholds, and yes, those thresholds are not based on the legal code anymore. We still value not murdering, lying and stealing, but those are downstream effects of sin, not the root. Christ is interested in the root, which is of the heart.
God's way is the way to know Him and Jesus by experiencing embodying His character traits, which is the narrow way to eternal life (John 17:3), and God's character traits are the deeper values that are the basis for morality. It would be overwhelming to us for God to exhaustively teach us how to embody His character traits in ever possible situation, so the point is to teach us how to embody them by teaching us a limited set of instructions that all have them in common. If we correctly understand a character trait, then it will lead us to take actions that embody it in accordance with God's instructions even in situations that God's instructions do not specifically address, but correctly understanding a character trait will never lead us away from following the instructions that were given to teach us how to embody it.
Asking "is do not murder" a sin or not is the wrong question. of course it is, but it is no longer positioned as a moral threshold as the new understands the act of sin happening long before the act of murder. murder is still sinful, but it is no longer a moral threshold so based on moral thresholds, the 10 no longer hold. Murdering does not bar me from salvation (albeit reflects an egregious state of my heart), and not murdering also does not guarantee me salvation (and my heart may still be in an egregious state). So where the 10 are principally good, their legal code is no longer binding. This shouldn't be confused with we are allowed to murder, steal and lie, but rather murdering, stealing and lying are no longer the thresholds.
Sin is what is contrary to God's character traits such as with unrighteousness being sin and sin is the transgression of the Law of God because it was given in order to teach us how to embody His character traits. Nowhere does the Bible say that murder is no longer are moral threshold or that the 10 no longer hold. Jesus saves us from our sin (Matthew 1:21), so him graciously teaching us to be a doer of the Law of God is intrinsically the way that he is giving us his gift of saving us from not being a doer of it.
So Is sabbath fulfilled? That needs unpacking as that wording can be used as a strawman. Sabbath legal code is fulfilled. The threshold for keeping sabbath holy was a prohibition of work, but that threshold is not good enough, and we know the prohibition of work itself is not what gives us rest. The Sabbath legal code is a physical analog for a spiritual principle (just like circumcision and the sacrafice). look at the animals, they are commanded to rest too, but not because they take rest (they have no authority to take rest themselves), but because it is given to them by one with authority. There is only one with the authority to give the rest we seek. He claims the title himself in "Lord of the Sabbath," which is an authority claim, not merely a title. So what is kept holy? The creation account is a salvation metaphor where we are the dark vessels, light is spoken into and a work is started in us that ends in rest and calling us Holy (2 Cor 4:6 affirms this). To keep us holy, we do not stop work once a week; we put our faith in Christ, who makes us holy.
We embody what we believe to be true about God through our works such as with James 2:18 saying that he would show his faith through his works, or in other words, the way to believe in God is by walking in His way. For example, by being a doer of good works in obedience to God's law we are embodying His goodness, which is why our good works bring glory to Him (Matthew 5:16), and by embodying God's goodness we are also embodying the belief that God is good. Likewise, the way to believe that God is compassionate is by being compassionate (Luke. 6:36), the way to believe that God is holy is by being a doer of His instructions for how to be holy as He is holy (1 Peter 1:16), and so forth, which includes keeping God's Sabbaths holy (Leviticus 19:2-3). The only way that we should cease to follow God's instructions for how to be holy as He is holy would be if He were to cease to be holy.
This is also exactly the same as the way to believe in the Son, who is the radiance of God's glory and the exact likeness of His character (Hebrews 1:3), which he embodied through his works by setting a sinless example for us to follow of how to walk in obedience to the Law of God. This also why there are many verses that connect tour belief in God with our obedience to Him, such as with Revelation 14:12 where those who kept faith in Jesus are the same as those who kept God's commandments and it is by this faith alone that we are made righteous and holy and attain the other character traits of God. To have a character trait means to be a doer of works that embody that traits, so it would be contradictory for someone to be made holy apart from being made into someone who is a doer of God's instructions for how to be holy as He is holy.
The legal code of the 4th has been made obsolete as is the entire 10 commandments and law. not to say that we are free to sin (which is a strawman), if law is made obsolete doesn't mean we are lawless, it means we are under a better way.
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, so if faith in Christ involved doing something different that was not cumulative with keeping the Sabbath holy, then it could not make it obsolete.