I don’t think so. I can’t think of another actor in that time that would have been a better fit for the role.

Arguably worse. Donnie Darko owes some of its success to Gyllenhaal’s quirkiness.

I guess if you got Freddie Highmore (Bates Model, The Good Doctor), but he was 9 when Darko came out. So, also no.

Richard Kelly (writer/director) seemed to think the movie would be better if they just explained everything. And that’s why we don’t like the Director’s Cut. I think it was done before but a lot of people had to have it explained to them.

I thought it was fine with him?

Nick Cage, that goes for any movie as well.