1)Never commanded by Jesus, even with plenty of opportunities.
The sabbath commandment was written by Christ at Sinai, with his own finger, before he became incarnate.
2)Never mentioned as a sin in the New Testament when sins are listed (breaking the Sabbath that is)
Sure it is:
1Jo 3:4 Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law.
The sabbath is part of God's law. Transgressing it is the same as idolatry or taking God's name in vain.
3)The other 9 commandments are rementioned in the New Testament, but the "Remember the Sabbath" is not.
Sure it is:
Luk 23:56 And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment.
4)Moral laws are "written on the heart" (Ask any "lost tribesman" what murder is, and then ask what keeping the Sabbath is)
Every human alive was born a sinner. There is no moral law written on anyone's heart, except those who have God's holy spirit. The scripture you're referring to is describing this event.
5)Jesus "broke" the Sabbath (only in the Pharisee's eyes because the failed to recognize that Jesus is the Lord of the Sabbath). Read John 9:15 and ask yourself why Jesus did not speak against those accusations?
Jesus didn't break the sabbath. It's impossible for him to sin. He did violate manmade, hypocritical rules created and instituted by men, but he never broke the scriptural sabbath.
6)No where in the OT or NT is the Sabbath given for all mankind to keep perpetually. Rather it is given to a specific nation at a specific time until Christ. (Galatians 3:19)
You're right. Only those who worship the one, true God were commanded to keep the sabbath perpetually. In fact, God established a special covenant for this purpose:
Exo 31:16 Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.
I'm not sure why you keep bringing up the sabbath in response to how long Jesus was in the grave, but I'm going to break this into two posts to separate the issues.