Owl to Zuko
Europe has wizarding duels, I've observed. They seem to be to the death or unconsciousness as well, though I've yet to witness a real wizarding duel at this school. And those duels focus around magic performed via wands anyway, not unarmed combat.
You're using the past tense. Does that mean you don't want to go back anymore? I wouldn't blame you if you didn't. I have to admit, the situation confuses me -- you care too much for him, or respect him too much, to strike him in a duel. That gets you exiled. Your father is unlikely to revoke your exile because he doesn't think you're a threat, but he also did not exile you because he thought you were a threat but rather, because you weren't a threat.
Is that a reasonable summary?
Maybe you'll find a new breed of dragons. If there are hybrids, however rare they might be, there could be other undiscovered species of dragons as well.