This, on both counts.The mosquito is notorious for reliability issues.
Ruger MKs or Browning Buckmarks are top notch rimfire pistols.
Think we've narrowed it down to a 9mm . Looking at glock ,springfield and s&w .
Unless it's gonna be a surprise, you might want to get him involved at this point to make the final decision.
The lot of pistols you just mentioned would all suit him well.
I'd actually give the advantage to the Glock overall, as the product support is going to be the best due to their popularity. Go with a Gen 4 if you take that route, as you'll have better luck with comfort (new backstrap options) and the mag release is infinitely better than previous Generations. They're also the easiest to work on, so if you wanna do some trigger part/spring replacement and what not, it's not gonna be an afternoon/evening of cursing as you learn how to tear down and reassemble the thing.