I think that (humanoid) Elementals can wield weapons, especially of a magical/elemental nature...
As for the whirlwind issue: I agree that, yes, the whirlwind can fling objects about, but not with any accuracy. Now as far as the issue with the amount of the debris, likely that's a GM call, and could go either way, really, depending on how s/he wants it played...I don't know of any *exact* rules for this....then again, I don't deal with elementals too frequently, either...