I strongly disagree with your comments on shotguns, but whole heartedly agree with your choice of handgun for the reasons stated.
1) Shotguns: Winchester makes several configurations of their Defender. It's a pump that has choice of stocks, an 18" barrel, 3" chamber, and holds 7 shots with 1 in the chamber. (It's good to leave the chamber empty and still have 6 in the hole so you make the unmistakable sound of racking the beast.) That's a gun which is easy to learn, aim/use, maintain, and will stop anybody without shooting up the neighborhood. Plus, you can buy a longer barrel and target shoot or hunt with it.
2) Pump vs semiauto: I've used a Browning 12 GA semiauto for 40 years and I can't tell you how many times I've had misfires or jams that required me to clear the chamber - but it's my skeet gun that I've used since I was 10, so I stuck with it - plus it's a Belgian Browning. I've had the same problems with my semiauto Colt .380 handgun, but never my S&W .44 revolver or pump Defender. Jams are frustrating when target practicing, but it's NOT what you want in an emergency. It's also more complicated to clean a semiauto. With a pump, as with a revolver, you don't have to worry about awkwardly clearing a misfire or jam. That's a BIG deal for a defensive weapon.
It's the same for the pump. Both types have a safety, etc.
For a gun owner like the OP, someone who won't even look at the gun after he buys it and fires it, a revolver is the only choice.
As far as size, even a shotgun w/18 inch barrel (one of my bedside guns is a Remington 870 express HD) is still a big gun. Fine for someone who takes the time to get and stay proficient, but that's not going to be the OP. He'll buy it, shoot it, and store it.