This is just an outright ignorant statement to make. The fact that the Sabbath is the last of the 4 commandments that determine how God is supposed to be loved and worshiped is what makes it a moral commandment. The fact that few people even keep this commandment only proves most professing Christians don't actually know Him, though they acknowledge His existence.
Knowing what God did in Gen. 1 and 2 isn't the same as personally knowing Him or even having a relationship with Him. Satan knows what God did, and none of that does him any good because he has no relationship with God. That's the whole point behind God going out of His way to identify the Sabbath command with the events of Gen. 1-2:3.
It literally makes no logical sense for you or anyone else to claim the Sabbath is only a representation of resting from sin while at the same time committing sin by trampling on the Sabbath. It is completely illogical, and it defeats the whole purpose behind resting from sin. This argument is tantamount to trying to wash a car with sewage.
When it comes to Paul mentioning a "law", a person has to be extremely careful in how they read his statements. Sometimes Paul refers to the 10 commandments, a specific commandment in that set, a sacrificial ritual, a man made custom/edict, or the Law(aka Torah) as a whole. The context of the passage usually reveals which one of those things he was referring to.
In Gal. 3:19, the "law" Paul speaks of is concerning animal sacrifices. This law was given to remind people of their guilt and that they needed a Savior that could wipe their slate clean through faith in His sacrifice. That's why Paul called this "law" a tutor. Paul was able to go a lot more in depth about this teaching in his letter to the Hebrews.
As to whether or not you should keep the Sabbath, the answer is a definite "yes" if you desire to truly follow God.
Your whole post here is full of lies, but i want to address this specific lie because it's the most important one that needs to be debunked. You say no commandment was made on the 7th day, but Gen. 2 says otherwise:
"Then God blessed the seventh day and sanctified it, because in it He rested from all His work which God had created and made." - Gen. 2:3
The very act of God setting the 7th day apart by blessing it, consecrating it, and stamping His presence on it by resting made it the Sabbath. The fact that God goes out of His way to mention this act in the codified version of the Sabbath command means this is when it was made. Jesus said the Sabbath was as old as the human race in Mar. 2:27, so there is no other event He could've been possibly been referring to.
Ancient Israel was both a church and state under the Sinai Covenant, so they were given the task of carrying out death sentences when certain laws were violated. As Rom. 13 teaches, the responsibility for carrying out death sentences is a purely civil matter, not a Church matter.
Under the New Covenant, people who reject the Sabbath are to to be treated like an unbeliever until they repent. The death penalty that was attached to the Sabbath command is symbolic of the death penalty that Christ will carry out on everyone who refuses to keep it come Judgement Day.
God commanded OT Israel to administer the death penalty for violating certain commandments because most of them didn't have God's Spirit and couldn't understand the seriousness of sin. The death penalty was both a warning and a doctrinal tool. True Christians don't need such reminders because they know how serious an offense profaning the Sabbath is to God, and they know how He will eventually deal with such people Himself.
Anti-Sabbatarians fail to understand this for the same reason most of the ancient Israelites didn't: they don't have the Holy Spirit, they fail to comprehend the gravity of sin, and they think they have better standards of morality than God. In other words, their religion is completely fake.