If everything were ideal, I'd also prefer the .357 and the 12 gauge.
I don't know how big bears get in your area but they've been killed here with .357's shooting cast bullets or Jacketed soft points. I'd stick with 158 grain or larger and with a bullet that will penetrate.
I also agree on the FMJ's for the 9mm and .40. Both are marginal at best but a black bear is generally not like a grizzly. Often they can be scared off by a loud noise and if not, something that penetrates will most likely get their attention or kill them. If you can find a truncated FMJ that would probably be better. If not, stick regular FMJ in there and keep the 12 gauge as close as possible. Remember, even a .357 is still a handgun. Most handguns are downright anemic compared to a rifle or shotgun with slugs, no matter what ammo you put in it. Plan accordingly.
I'd keep the 12 gauge loaded with all slugs. Some advocate staggering buck and slugs, the idea often being to shoot the buck into the bear's face to blind it, then shoot it with the slug to kill it. If I were primarily concerned with bears, I'd want to know that every round I worked into the chamber would be doing serious damage on impact and not just making superficial wounds.
I second the idea of contacting the local fish and game people. From what you've said, it sounds like something that they definitely need to be informed of and they would probably bring a trap out to relocate the bear to an area where it wouldn't be such a problem. That's the best way to deal with it. At the very least, it would create a paper trail in the event that they had to shoot it themselves - something to help them stay out of legal trouble if they are forced to kill it out of season and without a license.
The dog is also another great idea.
BTW - cast bullets are generally not recommended for polygonal rifling. IIRC, that's what all Kahr's have. Just an FYI.