Why do you believe the NT you have and quote from and interpret by sola scriptura isn't a 4th century (or for that matter a 16th century) fabrication, Blogger?
By faith in God. He promised to preserve His Word in Scripture. By faith, I believe He has done just that.
God preserved His Canon, not in a centralized organization in Rome, but through his universal church of all believers. All of God's local bodies of believers copied and passed the letters back and forth to one another and God preserved that which he wished to be preserved. In the end, a grouping of representatives from throughout all of the Christian realm gathered together and after prayer wrote down which books were canonical. By faith, I believe that they were inspired by God when doing so.
I have never claimed that councils were always wrong or unscriptural. Many times, they were led by people who truly wanted to honor and obey the Lord. And, just as God inspired men through plenary verbal inspiration to write Scripture, He preserved it through working through human beings.
These human beings, can fail. They can err. They can distort. We've seen throughout history various church leaders who were not leaning upon the Lord for guidance but rather were there because of personal ambition or because they were the second sons of European Aristocracy.
When the various local bodies of believers which make up the universal Church are led by people who speak that which is contrary to Scripture, I reject that leadership. Again, even Paul commended the Bereans for checking what he said in comparison to Scripture - so there is a precedent set.