Scripture is very clear that with the coming of the New Covenant, the Old Covenant passes away... all of it, Commandments especially.
For example:
Eph. 2:14-16 (ESV) 14 For he himself is our peace, who has made us both one and has broken down in his flesh the dividing wall of hostility 15 by abolishing the law of commandments expressed in ordinances, that he might create in himself one new man in place of the two, so making peace, 16 and might reconcile us both to God in one body through the cross, thereby killing the hostility.
Abolished the law of commandments expressed in ordinances..
This is not the weekly sabbath.
Jesus said to keep the commandments, and it is important to get it right. We have an avocate with the Father and you are right "we can't keep the law perfectly, we need the help of Jesus."
If the law is written on your heart does that include the sabbath commandment?
Jesus gives us His righteousness which is perfect. We can be justified before God as if we never sinned. But Jesus wants to write the commandments on our heart too. We can be sanctified through Jesus.
Rom 6:16 Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?
Rom 8:3-4
3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh: 4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
It is possible for the righteousness of the law to be fulfilled in us. By faith in Jesus