You already have what you need. The shotgun. As long as the bad guy isn't on top of you, meaning you didn't react soon enough, the shotgun will be the most rounded weapon you can have. You don't need to be as accurate with it as you do a handgun, and the point and shoot interface doesn't get much simpler.
The shotgun is a good choice to lie in wait with if you are actually in danger. Better to wait in ambush than to go looking for trouble. It increases your odds of surviving. A little thing I refer to as tactical planning.
A handgun can be a good alternative. They are better for sweeping enclosed places. That would be the weapon you want to use to check things out with.
For handgun ammunition I would stay away from Glasers. They are overpriced crap. A good hollowpoint round, or modified hollow point would be better. The Hornady Critical Defense rounds or the Federal Hydra-Shok rounds would be better options.