I've had similar problems with prehung doors whose hinges are set such that only one screw can hit the adjoining stud, and even that one only catches about 3/16" of the stud. For a new doorway, I rip a 2x to 4" wide, giving me a jack stud which winds up flush with the drywall on the inside of the door. For an existing doorway, I glue-and-screw 1/2" thick pieces ripped from a 2x4 onto the existing stud at the hinge locations. The doorframe is placed as close to the stud as possible when the door is hung, and the drywall butts against the stud. (In old work, the existing drywall is notched around the pieces.) The case molding covers the edge of the stud or the pieces.
This is not as much work as it seems, and the resulting door installation is very solid. I think the OP could use a similar technique to build out the jamb where the bolt goes through, and strengthen it considerably. Don't know how he might finish it, but there are several options. If that wall is fairly short, just fur out the entire wall that way and sheetrock it; if not, just make the extra woodwork around the door as attractive as possible.
Another door tip - for some reason known only to God and Stanley, the "standard" screws used in most door hinges are #9 screws. Try to find 2 1/2" long #9 brass, Philips-head screws anywhere. However, Grabber makes a #9 yellow zinc, square-drive screw in 2 1/2", 2 3/4", and 3" lengths that make dandy hinge screws (
http://grabberman.com). Probably not as much shear strength as a wood screw, but in my experience the screw pulls out of the jamb (or the door) long before the shear strength is tested.
As for the snakes -- be happy they aren't rats. Snakes are your friends.