As for the F, I think that's a bit more clear. As I mentioned, the main point of his day off is to get Cameron to loosen up. It's almost all for Cameron. So much so that when Cameron tells him he hasn't done anything fun Ferris is shattered, and instead of telling Cameron to fuck off like I think most ENTPs would, he goes even further to show him a good time. He's clearly extremely concerned about what's going to happen to Cameron if he doesn't change.
So maybe it isn't an absolutely clearcut case. I'm sure I could put forward a plausible case for him being an ENTP as well. But, on the whole, I think ENFJ is his best fit. He's charismatic (see the concern of the whole school over his illness) which ENFJs often are. He cares about his friends and wants to see them improve. He has remarkable foresight and planning. And the sheer volume of events he squeezes into his day off says J to me.
Hmm, I may have to watch it again.