"Very little, and often nothing, of what any pope speaks or writes is infallible."
Quantity has very little to do with it. Filioque, although inserted many years before the more refined doctrines of infallibility, was none the less inserted into the Nicene Creed (itself well defined statements of the entire body of Christ...including the Roman Bishop) with the spirit of infallibility. Theologians could argue that it was this prideful spirit which innovated this insertion into Christ words that ultimately necessitated the need to claim Papal infallibility.
Mechanics of infallibility are equally meaningless. St Peter, when siding with the Circumcision, was rebuked by St Paul (see Gal 2:11-16). And yet, even a millennium after the erroneous Filioque entry, which Rome ultimately had to justify with infallibility, which Rome realized later was not in the original language used by any of the Gospels, has yet to repent and set the record straight.
The point is, you cannot use the vast cumulative output of the popes to look for statements that infallibly deny infallibility, as you attempted.
I do not think the dual procession of the Holy Ghost has been defined infallibly. Further movement on this doctrine is possible, and, given some intriguing passages in the recent Deus Caritas Est, likely.