You are wrong. Shooting to stop is not shooting to kill. Shooting to stop is exactly what it means, to stop whether the person drops to the floor or turns and runs. Never say the word 'kill' after a self defence shooting.
If they turn and run, yea, you're not going to want to shoot them in the back.
But if someone is facing you and threatening you with a weapon, you bet your ass you want the highest probability of killing them. You guys do realize people have successfully sued homeowners for shooting them, right?
Yeah, the family can sue, too. But the events are going to be a bit...one-sided. A 'he said; he's dead' argument, if you will.
I wouldn't recommend slugs because of massive overpenetration and requirement for both precise center mass shots and luck.
To the guy asking about a HD shotgun: Maverick 88 is cheap, lightweight, and reliable. Personally, I think the 500 is a waste of money for a 'closet gun.' The 870 is probably the better pump, but it's the most expensive. And heavy.
As someone else said, though, best not to put a pump shotgun in the hands of a novice. It's a good reliable weapon, yes. But it takes practice to be able to maneuver in tighter spaces and reflexively rack the pump quickly and efficiently after every shot.
For a single home defense weapon, for someone who's not a regular shooter- large .38 revolver with non-cowboy grips. Colt Official Police size or similar, but with a molded grip with finger grooves.
Full-size 9mm auto works well, too, but you need a little more practice and the gun needs more maintenance. A good DA revolver can go in a drawer for a few years, and as long as it went in working, that's how it's going to come out.