Where are you getting your theology? It sure isn't from God's word since the phrase "law of sin" is not found in any translation I am aware of. When Paul writes about the Law, he is writing about the Law that God gave to Moses. As to Peter's vision concerning eating unclean foods, he explains this vision in Acts 10:
Acts 10:28-29
28 And he said to them, "You yourselves know how unlawful it is for a man who is a Jew to associate with a foreigner or to visit him; and yet God has shown me that I should not call any man unholy or unclean. 29 "That is why I came without even raising any objection when I was sent for. NAS
Now lets move to Acts 15 and the Jerusalem council that was called because Judaizers insisted the gentiles be circumcised per the law.
Acts 15:23-29
"The apostles and the brethren who are elders, to the brethren in Antioch and Syria and Cilicia who are from the Gentiles, greetings.
24 "Since we have heard that some of our number to whom we gave no instruction have disturbed you with their words, unsettling your souls, 25 it seemed good to us, having become of one mind, to select men to send to you with our beloved Barnabas and Paul, 26 men who have risked their lives for the name of our Lord Jesus Christ.
27 "Therefore we have sent Judas and Silas, who themselves will also report the same things by word of mouth.
28 "For it seemed good to the Holy Spirit and to us to lay upon you no greater burden than these essentials: 29 that you abstain from things sacrificed to idols and from blood and from things strangled and from fornication; if you keep yourselves free from such things, you will do well. Farewell. " NAS
Now if you are going to quote the Lord at least quote Him correctly:
Matthew 5:18
18 "For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass away from the Law, until all is accomplished. NAS
People do not fulfill law, they obey law. Jesus did not fulfill the Law, He fulfilled the prophesies concerning the suffering Messiah and at His second advent will fulfill the balance of the Messianic prophesies concerning the conquering Messiah.
Man's spirit comes from God.
Ecclesiastes 12:6-8
6 Remember Him before the silver cord is broken and the golden bowl is crushed, the pitcher by the well is shattered and the wheel at the cistern is crushed; 7 then the dust will return to the earth as it was, and the spirit will return to God who gave it. 8 "Vanity of vanities," says the Preacher, "all is vanity!" NAS
When we are born again we are sealed with God's Holy Spirit. So you are confusing "spirit" with "Spirit".