You have a misunderstanding of the covenants. You seem to confuse the old covenant, ratified at Sinai, with the entire collection of books called the "old testament". They are not one and the same. Paul based all of his understanding upon the only scripture he knew...the books of the "old" testament.
Paul knew what that New Covenant entailed, even if it was not written down yet. The OT is not obsolete; its interpretation and practices are.
Doug you have some kind of a gnostic religion . You assume that in the 1900+ years since Christ the Church was all wrong... the secret is really in the lost tribes and law keeping and a denial of the trinity.....etc etc...
The Gospels are Old testament . The entirety of the gospels is Old Testament. they functioned and lived under the law.
The New testament began at the death and resurrection of Christ . Paul taught that men were free from the law .
The heavens have opened Doug, the curtain rent, a sheet has been lowered to show you that there is no more clean and unclean
The words of Christ ring out with the only Holy remembrance He has ordained ... "Do this in memory of me"
The passover was gone, and in its place a new remembrance.
So you can go back and try to please God and try to be holy by redoing what He has called finished . It will not save you, it does not make you holy to doubt the work of Christ..
Gal 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
Gal 3:10 For as many as are of the works of the law are under the curse: for it is written, Cursed [is] every one that continueth not in all things which are written in the book of the law to do them.
Gal 3:11 But that no man is justified by the law in the sight of God, [it is] evident: for, The just shall live by faith.
Gal 3:12 And the law is not of faith: but, The man that doeth them shall live in them.
By placing yourself under the law, you now must do the impossible... you now must keep it PERFECTLY , you will be judged as you have chosen. Not on the perfectness of Christi or His righteousness.. but by your inability to keep it PERFECTLY and you will fail Doug
Jam 2:10 For whosoever shall keep the whole law, and yet offend in one [point], he is guilty of all.
The purpose of the law was to show us we needed a Saviour.
Gal 3:24 — Wherefore the law was our schoolmaster [to bring us] unto Christ, that we might be justified by faith.
Doug, your righteousness is as filthy rags before our holy God
I chose Christ !!