Then why did the Catholic church canonize it?
And why do Catholics then consider the Gospels superior to Paul's letters?
And if the writings of Scripture are that likely to be subject to error, then why are the traditions of the Catholic church not considered to be so?
The Catholic Church developed the canon of the New Testament, a canon which is still accepted by all Christians. They determined which books went in and which didn't.
And why do Catholics then consider the Gospels superior to Paul's letters?
I think superior is probably the wrong term. I think it would be more accurate to say that Catholics do not show the preference for Pauline epistles that a minority of Protestants do.
And if the writings of Scripture are that likely to be subject to error,
Where have I EVER said that?
then why are the traditions of the Catholic church not considered to be so?
The Catholic Church has NEVER said this.
The Catholic Church acknowledges a "hierarchy of the truths of faith" of the Revealed Word. At the pinnacle of these are the Gospels which contain the words actually spoken by Christ and are perfectly summarized in the Beatitudes. Everything else in the Revealed Word was either in preparation for or in support of the Gospels.