Wow, this is one long thread. Couldn't get through the whole thing. Two points, and sorry if I missed some posts, but there's only really two "survival" situations, wilderness survival, which is something I'm "into", and then the end of the world as we know it survival. The big Boogaloo...the Big Rumble!
For wilderness survival, I think the .22mag is good, I just wish there was a wide variety of sub-loads that mimic .22 long-rifle loads, especially the very low powered ammo like the CCI "Quiet" ammo. If there was, I would get a .22mag. If you live in bear country, you might want to pair it with a .357 or .44/.45 handgun.
For the end of the world a .22mag would "do", depending on what your imagination says the end of the world looks like, but it kind of pushes my buttons when people start saying that this or that caliber is "better" because it can be "scrounged", or worse yet, will be more "available". The ONLY ammo you will be able to obtain, is what you already have. No one will be parting with ammo, and if you found someone that was willing to trade, the cost will be tremendous. Willing to trade seven days of hard labor for six rounds of .357? If you have a 6.5 Japanese Rifle, and 5,000 rounds of ammo for it, you are better off than the guy with an AR and 4000 rounds of ammo. Even if you both have 1000 rounds, you are both out of ammo, when that ammo is gone, with no resupply. Out. Gone. Nada. Zip. Caliber "does not matter".
So, for the end of the world, the collapse of civilization, the big rumble, choose any caliber, but have lots of ammo in that caliber. There will not be more. You will not "scrounge". No "ammo for sale" sidewalk stands.