I didn't get the feeling that he's batman. He's always been a wimp.

He's just got a hero complex, now has the power to back it up, but is burning out nonetheless because his body can't keep up with the responsibility that everybody has placed on him (including himself).

It's similar to every other "I can't rely on my friends or else I'll hurt them" anime scenario, except this one's kind of baked into his character from the start.