those plans are great. now you have a door that can not be busted in. what about the weak wall on eather side of that door?
most walls have a piece of 1/2 plywood on the outside of the studs, some kind of siding over the plywood and 1/2 sheetrock on the inside of the studs. that is the weak point of any home.
Buy a concrete home. then it would be worth reinforcing the doors.