How much of this Catholic stuff is actual from the Bible?
The Dominicans are preachers and they study scripture. That is in the Bible. There is much in the Bible about pride and humility.
He must increase, but I must decrease.” John CH 3
Catherine of Siena is not in the Bible because she died in 1380 AD.
“no one is obligated to believe that a particular person (someone not referred to in Tradition or Scripture) is a Saint”
Of course, if one believes that there is no such thing as a saint, that would be contrary to the Gospel.
“Now the Saints who are mentioned in Scripture, such as Saint Peter the Apostle, are a separate case. Since their lives and holiness is attested to in infallible Divine Revelation, the Church can teach their holiness and can declare them to be Saints. For unless a Saint is mentioned in Sacred Scripture , such a Saint’s canonization cannot be considered a part of the teachings of the Church. .”