Modifying the toughness powers to mental instead of physical should be easy enough.
For the gun you could modify something like inhuman strength/speed to... let's call it inhuman aim:
[-2]Inhuman Aim:
Trickshot
Whenever you try to shot shoot inanimate objects, you gain +2 to your guns roll. (similar to "improved lifting" from inhuman strength)
True aim
Difficulty factors due to a targets cover are reduced by 2 (similar to "almost to fast to see" on inhuman speed)
Bullseye
Attacks made with the gun inflict +2 damage, increasing the stress made by 2 on a successful hit. (similar to "hammer blows" on inhuman strength)
Winter's Chill
The bullets from your gun are made from the magic of the winter court, removing the need to reload at all and satisfying the catch of summer (because it still needed the summer catch thing, and a magical gun should not go empty, in my opinion. Either way, it is mostly cosmetic, since bulletcounting is not really encouraged anyway.)