Shalom, Big Boy Johnson.
Actually, while the COVENANT was improved, the LAW has NEVER been rescinded. Instead, we read ...
Jeremiah 31:31-34 (KJV)
31 "Behold, the days come," saith the LORD, "that I will make a new covenant with the house of Israel, and with the house of Judah: 32 Not according to the covenant that I made with their fathers in the day [that] I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them," saith the LORD: 33 "But this [shall be] the covenant that I will make with the house of Israel; After those days," saith the LORD, "I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. 34 And they shall teach no more every man his neighbour, and every man his brother, saying,
"'Know the LORD':
"for they shall ALL know me, from the least of them unto the greatest of them," saith the LORD: "for I will forgive their iniquity, and I will remember their sin no more."
We call this the New Covenant, but one should note that the New Covenant is between God and "the house of Israel, and with the house of Judah." It's not with Gentiles at all, unless they count themselves among the children of Israel through the Messiah.
Technically, Mosheh ("Moses") was never the high priest; his brother 'Aharown ("Aaron") was the high priest, and each son or grandson in his lineage who was selected to be the next high priest could only do so between the ages of 30 and 50.
Actually, this is not true. Again, Mosheh was NEVER the high priest, and Yeeshuwa` haMaashiyach ("Jesus the Christ") never changed the Law. He REINFORCED the Law of His Father, and showed that it was actually much stricter than they assumed it to be! God's Law consists of 613 commandments, and Yeeshuwa` succinctly summed these up into two commandments:
Matthew 22:34-40 (KJV)
34 But when the Pharisees had heard that he had put the Sadducees to silence, they were gathered together. 35 Then one of them, [which was] a lawyer, asked [him a question], tempting him, and saying,
36 "Master, which [is] the great commandment in the law?"
37 Jesus said unto him,
"Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. 38 This is the first and great commandment. 39 And the second [is] like unto it, Thou shalt love thy neighbour as thyself. 40 On these two commandments hang all the law and the prophets."
Yeeshuwa` also said,
Matthew 5:17-20 (KJV)
17 "Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil! 18 For verily I say unto you, Till heaven and earth pass, one jot (the Hebrew letter yod [י]) or one tittle (a "thorn" that makes the difference between a dalet [ד] and a reish [ר], for instance) shall in no wise pass from the law, till all be fulfilled. 19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach [them], the same shall be called great in the kingdom of heaven. 20 For I say unto you, That except your righteousness shall exceed [the righteousness] of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven."
You're not wrong regarding justification; one cannot justify himself by keeping the Law. One must be justified by God alone.
Again, you're not wrong, but the Law of the MESSIAH (the Christ) of God is the SAME as the Law of His Father, YHWH.
There's no problem with worshipping YHWH God on the Shabbat ("sabbath"). We SHALL be required to worship Him on the Shabbat. But, we should be talking to Him and bending the knee to Him EVERY DAY!