I think your approach to animation is great so far. But I believe you can go even farther. I mean look at animators like Don Blooth and Miyazaki. The animation from these two are just amazing and I bet you can be just as good as they are.
If I had to pick one of the first four I would say animation as it forces you to abosultyelty understand movement much more then the others while the others ones all have skills that overlap with animation skills I think while animation again has that extra in depth focus on undertsnading movement
illustration animation more mangas concept art other
hmmmmm I feel all of the first for are kind of inter related for you in that they all seem to related to your careers goals as far as I can tell and all have skill overlap that would benefit each other....hmmm I guess I shall vote other
I am on that. Both complex illustration and animation takes just as much time. >.> Except for complex illustration ppl stare at it for 2 seconds and fav, good animation end up being 2-3 seconds on screen. lol