You still don't understand what papal infallibility means. An infallible pronouncement—whether made by the pope alone or by an ecumenical council—usually is made only when some doctrine has been called into question. Most doctrines have never been doubted by the large majority of Catholics. Most Protestants (yes, despite your claim to the contrary, you ARE a Protestant) believe that infallibility means the pope can never err or sin. This is not the case. Indeed, infallibility also belongs to the body of bishops as a whole, when, in doctrinal unity with the pope, they solemnly teach a doctrine as true. What infallibility does do is prevent a pope from solemnly and formally teaching as "truth" something that is, in fact, error. It does not help him know what is true, nor does it "inspire" him to teach what is true. He has to learn the truth the way we all do—through study.
Pope Joan? This has been thoroughly and repeatedly debunked. A google search will give you more info than you have time to read. Take those blinders off and actually learn what the Catholic Church really teaches. I was a Baptist for a long time and believed The Trail of Blood was accurate. Read for yourself a different viewpoint from what we were taught:
http://www.catholic-convert.com/wp-content/uploads/Documents/TrailOfBlood.pdf
However, as far as your misunderstanding of papal infallibility, often those who object to the doctrine of infallibility confuse it with impeccability or personal inerrancy. It is neither. Impeccability means that a person is incapable of sinning. Popes, like other Christians, are sinners. Personal inerrancy means that Popes cannot make mistakes. Infallibility, on the other hand, refers on to that guidance of the Holy Spirit that guards Popes from officially teaching error in matters of faith and morals. The foundational elements of the doctrine embody the following points. First, Jesus established Peter in a dynastic office as head of the apostles and empowered him with his authority in deciding matters of faith and morals. Secondly, Jesus intended that this office and authority be passed on to Peter's successors. Matthew 16:16-19