1. Such power pretty much ends-up being a super-blanket, meaning the ice, although cold, cannot cool anything else until the effect is dispelled. Also would grant total thermal immuity unless to save mana, it only protects the vitals.

2. In marvel comics, it's implied that power-users are immune to their own powers. So no burst eardrums or shredded vocal-cords for Banshee. Likewise, Cyclops's eyelids are bazooka-proof.