Sorry, but you still haven't proven that Leo thought you could sell people out of purgatory. You've demonstrated that he was a sinner who grasped after money - ok. No one argues that point. But you need to produce a teaching document from Leo in which he says you can sell or buy people out of purgatory.
Paul called himself a sinner but wrote inerrant Scripture. So did all the prophets and the apostles.
Infallibility is not impeccability. Infallibility means you'll never teach error. Impeccability means you'll never sin. I can be the biggest sinner in the world and still teach infallibly. The existence of Scripture proves that. In fact, any sin I commit is WORSE precisely because I KNOW the truth.
I don't know why you guys have such a tough time with this. All the prophets and apostles were in exactly the same position as the Pope, and you accept all the writings of the prophets and apostles. It's not like there isn't tons of precedence for this concept.
I don't need to prove anything. History stands on it's own and men's desires are clearly visible.
There is a difference between personal sin and teaching heresy. Papal infallibility is proven false by this directive Leo was pushing. Leo was pushing the sale of indulgences to finance St.Peter's. I don't need to define indulgences for us. To bilk the impoverished peasantry out of the meager wealth they possessed to build pretty buildings and buy pretty painting is deplorable and evil.