I have copied the content of your posting and forwarded it to the gun dealer that I worked with when I bought this place. I will post back when he replies to me later in the day. I do know a couple of things, at least as they apply to feral hogs and smaller 4 legged varmints that we have to deal with here in West Texas. A .22 is going to be pretty much useless unless you are an incredibly good aim and concentrate on head shots. They might be o.k. for item #1 in your list but that would be about it. A shotgun may or may not be useful for item #2 but the last thing you want in those cases is to use a shotgun and only wound. First, you don't want an angry wounded bear coming after you. Second, in all cases you want to kill as instantly as possible. You don't want to wound and have the animal run away only to suffer. A shotgun using slugs as opposed to buckshot might work however. Hunting deer is obviously a really big thing here in West Texas and hunters take their choice of weapons very serious. I don't hunt so I can not answer that but my dealer will.
The 22 has been used to kill more farm critters than any other round in existence plus probably an equal number of large game not to mention squirrels and bunnies. I know have both witnessed and done in critters up to 1500 pound weight. Of course usually the dispatch of farm stock is usually in a confinement situation with the spot placed by muzzle contact usually immediately followed by sticking. Though my father much preferred to drop beeves from the side at some distance so the critter didn't land on him. Seriously there is a spot just behind the eye that is a direct route to the brain pan. I can still hear CRACK/WHUMP of the shot and a half ton of beef collapsing.
I also don't think you've garnered as much experience as I with the 12 gauge. Put this way I'll take my M37 Ithaca and breneke 1 1/8 oz slugs and take on all comers end zone to end zone. A well placed ounce plus chunk of lead at 1300fps is a DRT round. Doubt me, ask bear guides in the north woods what they like to tote.