I am going to wholeheartedly agree with this. Security system or a tall electrified fence. Something strong enough to **** him up, but not enough to kill. Also, motion detector lights EVERYWHERE. They are super annoying in the country but will allow the dogs to handle it as they see fit - you're a brilliant trainer and I think with a little work you could establish that animals are not something to bark at, but people are something to flip out over. After about a year or so the local animals start avoiding the lights, so eventually that wouldn't be a problem.
If you do decide on the dog, my vote is Fila. I don't want to jump on the blind "EVERYONE should get a Fila because they're so awesome!!1!!1" bandwagon we had going a few years ago, but they seem like the obvious choice. They have the least cons. They literally can do everything you listed and then some. They are hopelessly devoted to their families, especially their kids. They were bred to herd, guard, track, and take down threats without killing them. (It would probably cause more problems than it would solve if FutureDog stepped past the alerting and threat display only to kill or maim the douchecanoe. It would serve him right, of course, but you don't want to have to hide a body or explain to the kids why their dog is being PTS.)
The cons can be dealt with. Size? Get a female, keep her in a box, and feed her coffee.

They don't seem to eat much, though, so the only downside is going to be medication and ability to put into a two-seater. Too sharp? Your breeder can pick the right one from the litter or advise you against a certain breeding. That's a risk you run with a lot of breeds, anyway.
They are readily available to you through excellent breeders, you'll have support and boarding, and won't be crazy expensive. Plus, you can meet and evaluate the bitch and the dog for yourself. That would be enough to convince me.