You r logic is very contorted. No one said the 22 is the BEST carry caliber.
As for deer? That's a decision based on hundred year old data. For instance, in Florida I can hunt with any centerfire caliber .224 diameter and up. That means 25 acp is legal for deer. 22lr is leaps n bounds over 25acp.
Shoot the rapist till the magazine is empty, 22lr will take the 'rape' right out of a perp once he's taken a few shots to the 'tools' and an after or two.
My wife can empty all 10+1 of her ruger MkII into a 2" circle at farther than self defense range in about 8 seconds.
Keep thinking 22lr are harmless. They are like real estate..location, location, location.
The guy is having trouble pulling the trigger. 22s have triggers. He is also having trouble pulling back hammer for single action.
A different shapped hammer, grip, or slide, may help.
I like the idea of 1911, if he can get one can work the slide on or, something on it to help. I also like idea of different hammers, and grips. Small might help get a tight grip, same could be said for big grips for some.
Hogue grips can change the black hawks grip similar to double action, but it won't roll in his hand, which can help in cocking. Double action revolvers have less hammer travel.
Trying some custom triggers may be interesting. Handling lots of gun and going store to store, could be fun if he has the time.
If one of his guns he likes, he could get trigger gauge, and measure the poundage.
Is a long gun easier or worse? For semi auto rifle he could get something with big knob on slide. They also make pistol grips for racking pump shotgun.
If there is a big gun shop nearby, I would go there when dead.