Does the Deadly Aim feat work with firearm attacks? I know that it does for the outside of the touch range, but what about the touch range of the firearm?
Yes. Firearm targeting rules specifically indicate that they aren't actually Touch attacks; they just roll against Touch AC. This means that Deadly Aim will still work with firearm attacks. However, if you had a hypothetical feat that gave an attack bonus on Touch attacks specifically, it would not work for Firearms.