The covenant was ratified by His blood, the covenant is God's laws written in the heart Heb8:10. Without blood a covenant could not be ratified.
Paul's writings is very much Scripture, but in the inspired Scripture we were warned what people would do with them
2Peter 3: 15 and consider that the longsuffering of our Lord is salvation—as also our beloved brother Paul, according to the wisdom given to him, has written to you, 16 as also in all his epistles, speaking in them of these things, in which are some things hard to understand, which untaught and unstable people twist to their own destruction, as they do also the rest of the Scriptures.
This is a salvation warning so his writings should be carefully and prayerfully studied and not make something Jesus said was made for mankind, make Paul teach is against mankind. Pauls Scriptures should be harmony with Christ, not against what He taught. We are not baptized in Paul's name, its not Pauls laws written in the NC believers heart, Paul can't save us, he can only lead us to Jesus and would never countermand what Jesus taught.