Well, they're catholic, they're not supposed to do more than look at those girls. And sipping wine! There's a specific part of the service when they get to do that. You're right, there are more than 20 missionaries at work simultaneously.I assume Chief Ragusa is referring to the slowness of missionary work, to pile up 110 ducats of missionary maintenance ( really, that should quite a handful of them sipping wine and watching the countryside girls instead of being preaching )
I'm far from expert in gameplay and mechanics and the like but... wouldn't be cheaper to take Humanist Tolerance than converting all those provinces?
What would be really cool, in this world gone mad, would be if one of the european minors had successfully landed in the New World, and because the natives never had to deal with massive colonization, that one European colony is instead a source of Latin tech and westernization, leading to the eventual formation of a modernized aztec empire that will bring England to it's knees.