If as you claim...why are you Roman Catholic and follow the pope?
That's easy!
To quote Unam Sanctam, the bull which you love to quote out of context, the opening sentence is,
"Urged by faith, we are obliged to believe and to maintain that the Church is one, holy, catholic, and also apostolic. We believe in her firmly and we confess with simplicity that outside of her there is neither salvation nor the remission of sins, as the Spouse in the Canticles [Sgs 6:8] proclaims: ‘One is my dove, my perfect one. She is the only one, the chosen of her who bore her,‘ and she represents one sole mystical body whose Head is Christ and the head of Christ is God [1 Cor 11:3]. In her then is one Lord, one faith, one baptism [Eph 4:5].
Catholics follow catholic popes, not heretics. There's been more than one pope in the history of the Catholic Church and one cannot obey two masters.