If you use Colossians 2:16-17, which you're interpreting incorrectly, to say that the Sabbath is void because it was nailed to a cross and crucified, then you must also include all of the other commandments being voided. Following your theology, murder and adultery are no longer sins and you're free to go do them at will.
Regardless of whatever else is written about no murder or adultery in other passages, you must admit that since the law has been crucified, as you say, then it doesn't matter what those other verses/passages say to the contrary.
If you try to tell me "murder is a sin" I can use Colossians 2:16-17 to prove that it isn't. As you and I both know, murder is still a sin. That means you're interpreting the Bible incorrectly with an anti-Sabbath bias.
Furthermore, the plain text reading of Colossians 2 doesn't void the Sabbath. What has been voided is practically everything else aside from the 10 Commandments.
Finally, Hebrews 4 plainly states the literal Sabbath is still in effect and is an act of disobedience to not keep it.
Hebrews 4
9There remains, then, a Sabbath-rest for the people of God;
10for anyone who enters God’s rest also rests from their works,
e just as God did from his.
11Let us, therefore, make every effort to enter that rest,
so that no one will perish by following their example of disobedience.
Obeying God isn't works-based salvation. Works-based salvation is following your own way, or the way of others, in order to gain God's favor and that isn't what God is impressed with.
Obeying God pleases God and it's good and is required for salvation; faith is only the first step of obedience in an eternal journey. That we don't have to obey God, that we can sin as much as we want, that the can abandon the faith after believing for a short time, that we can fully-convince ourselves and others that obeying God is somehow an error that leads to death, is a demonic deception in the church.
Romans 2
7To those who by
persistence in doing good seek glory, honor and
immortality,
he will give eternal life.
8But for those who are self-seeking and who reject the truth and follow evil, there will be wrath and anger.
Philippians 2
12Therefore, my dear friends,
as you have always obeyed—not only in my presence, but now much more in my absence—
continue to work out your salvation with fear and trembling,
13for it is God who works in you to will and to act in order to fulfill
his good purpose.
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