That's right, GOD'S word - Sacred Scripture. His revelation written down as He has done since Moses. God knows all too well the propensity of men to corrupt His truth and it's why Holy men of God spoke as they were moved by the Holy Spirit, they were written, copied, distributed and preserved. It is folly to imagine unwritten "traditions" are in any way comparable to Divine inspiration. Within a few decades after Christ ascended, His teachings and the continued revelation was being written down so that there would be a record to be used as both resource and rule of the faith. John's Revelation was the last of the New Testament books to be written.
There are first and second century writings of Christian leaders that teach and list the writings - as well as acknowledging their Divine origin - that were received by Christ's own that make up the NT and if all the manuscript copies of those books were destroyed, almost the entire NT could be reconstructed using their writings. The later councils did nothing more than confirm what was already believed by the church at large. The church was not dependent upon the decision of a council for the contents of the NT.
The ONLY "Petrine" authority was the same Apostolic authority Jesus gave to the other eleven and it was NOT something that could be handed down from an Apostle to his "successor" - ONLY Jesus anointed His Apostles. There was a handing down of the gospel truth and that was what determined if a man was speaking as from the Lord. Peter called Paul's epistles "Scripture", he didn't need to wait for a council to decide it for him three hundred years after he was martyred. Obedience was expected and those who would not were excluded from the fellowship.
". . . was NOT something that could be handed down from an Apostle to his "successor . . ."
No Seat of Moses in spite of what Jesus Christ Himself said, therefore no Seat of Peter.
Gotcha, another instance of Jesus Christ being in error.
The infallibility given to the early Church Fathers in sorting out what are the true words of God is the highest form of authority. This lasted for nearly 300 years over different popes when the canonical texts were approved in AD 382. That Petrine authority did not suddenly evaporate with the Reformation.
This is precisely why droves of pre-eminent Lutheran theologians have decamped and converted to Catholicism. This is the teaching of over 2000 years, the teaching accepted by the saints and martyrs of the Church and the brilliant minds of Augustine, Aquinas, Newman (a convert) and Benedict (called the “theological Einstein of our times) and one that is not open to confusing and contradictory interpretations from every branch and sub-brach of Protestantism.
This is why the brilliant essayist Hillaire Belloc wrote in his book “Heresies” (a copy of which I have with me), wrote that unlike other heresies, Protestantism “spawned a cluster of heresies.” Fortunately, leading Lutheran and Episcopalian theologians who have spent a lifetime of scholarship have realized the central errors of the Reformation and the logical nonsense it leads to. You have a First Baptist, First Presbyterian, First Emmanuel and every other kind of first class nonsense.