ive always imagined that instead of turning into their curse’s element unlike other curse users, the explosion curse user basically just has a self-destruct option if they wanna use it
Don’t think so, I think it’s just an innate ability they’re given, since Curse Users wouldn’t be able to feel harm if they were made purely of their Curse. (As seen by Morden after Julian)
The eye of the storm itself is calm and can be seen as a moment of Grace 
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Storms are constantly moving however, and the eyewall which surrounds the eye itself is the worst part of the storm