Just want to touch one quick thing on your post. I agree wholeheartedly that there were a lot of scummy Popes. If you find a Catholic who claims they were free of flaws, knock 'em on the head for me! But...I think you have an strange view of when "ex Cathedra" applies.
It is not normal for the Pope to speak "ex cathedra." Nowhere near everything he says qualifies for this status. In fact, most scholars believe such authority has been used only 7 times in the last 2000 years. Not a common occurance, by any strech. Wikipedia actually has a decent list:
- Tome to Flavian", Pope Leo I, 449, on the two natures in Christ, received by the Council of Chalcedon;
- Letter of Pope Agatho, 680, on the two wills of Christ, received by the Third Council of Constantinople;
- Benedictus Deus, Pope Benedict XII, 1336, on the beatific vision of the just prior to final judgment;
- Cum occasione, Pope Innocent X, 1653, condemning five propositions of Jansen as heretical;
- Auctorem fidei, Pope Pius VI, 1794, condemning seven Jansenist propositions of the Synod of Pistoia as heretical;
- Ineffabilis Deus, Pope Pius IX, 1854, defining the immaculate conception; and
- Munificentissimus Deus, Pope Pius XII, 1950, defining the assumption of Mary.
Now, if you'd like to have a discussion on any of these, feel free to ask, and I'm sure that there are many Catholic FReepers who would be more than willing to talk with you!
Incidentally, I can understand the difficulty with the Immaculate Conception going from scripture alone, but the Assumption is right there, Apoc. 12.