Fellows, believe it or not, I just read this "whole" post for the first time.
I can personally give some input here that may, or may not sway some of your thinking on the 22 or 22 magnum as a defensive caliber. Before I say it all though, please keep in mind that I lived a very violent childhood(home life), in an enviroment that seemed to breed trouble. I left home at 13, but for what ever reason, it took several more years to finally leave it all behind me, and make up my mind to live a more productive/peacable life style.
With that said...
I had a sister that was about a year younger than me. She opted to stay with our Mom who was then about as wild as a woman can get, and our pyscotic(spelling) step father who got his kicks from beating us, throwing knives, beer bottles, bricks, etc., at us, and yes occasionally shooting his trusty 9MM at us for such offences as walking in front of the TV while he was watching a show.
My sister had just moved out at 17 when she accidently walked in on a drug deal at a "friends" house, and was shot, and killed by a 22LR revolver. She was hit in the aorta(spelling), and was DOA after the 10 minute drive to the hospital. A couple years before that, I was shot point blank in the lower right chest by a 25 ACP, which hit a rib, chipped it, and glanced right back off, and out leaving nothing more than a small flesh wound, and me in a very bad mood which proved to be not too good for the shooter.
Three years later(I was 20 this time) I was once again somewhere I had no business being, and was shot in my left thigh with a semi-auto something. I'm assuming it was a 380 HP(possibly 9MM) after seeing the bullet fragments the doctor dug out of my leg. The bullet hit me straight on in the center of my middle thigh, busted on the bone without breaking it, and pretty much left shards of bullet jacket, and lead in that area which nearly bled me to death. I still managed to not only drive home, but out of fear of possible legal complications waited a full two days before seeking medical help. The doctor said another few hours of steady bleeding like I was, and I would've died.
I've always questioned "why" could a lowly 22LR take my sister away so quickly, and easily, when a 25 Auto to the chest only made me mad, and even a direct hit from a larger caliber that did tremendous damage to my left thigh(arteries included) still gave me two days with zero medical attention?
I guess I said all that to make this point;
I'm of the mind that I'll use what ever(22LR included) to defend myself, but I'd never carry anything less than at least a good 32 magnum for that specific purpose. A 357 magnum would be the smallest/lightest caliber I'd trust 100%, and even then, if I was ever in that position again, a 44 magnum would feel like it wasn't enough.
With a "perfect" shot/situation, any gun might do wonders for you, but there's a "very" real chance anything less than a well placed shot from a large caliber just might end with you, or your loved ones on the raw end of the deal.