Council of Nicaea. The Church teaches that both Scripture and tradition are authoritative.
Of course they do. It gives them authority.
I don't follow those who are self-proclaimed authority.
Tradition is not reliable enough to be authoritative. God saw fit to put what He knew we needed in a book. He's a big fan of writing things down. that way there's a permanent record of it and it can be used as a standard to verify it instead of assuming or counting on men having enough integrity to NOT corrupt what if being passed on by word of mouth. Because THAT certainly isn't going to work.