How can they 'smell' space? They live in a sealed environment. If they can smell space, surely they have a leak.

If he killed her and took her guns don't you think he could have taken a key?

Gun safes are tax exempt to promote purchasing. While I agree that may have hindered him. He would have found a way around it. He would have stolen a gun from someone else or bought one off the street. And not having drills is a mistake.