I'm only a casual watcher, so maybe this has been explained, but--
Nathan has no
tactile sense whatsoever except when he's in contact with Audrey? How does he live? Aside from the fact that he'd cut and bruise himself on a regular basis, how could he possibly drive when he can't tell how much pressure he's putting on the gas pedal? Or more importantly, the brake.
And I wouldn't trust him with a handgun. If you can't tell whether your finger is on the trigger without looking at it... if you can't tell how much pressure you're putting on the trigger until it goes off... that's just scary.