A revolver that gives him a DA option is a GREAT training tool for proper trigger control. Whenever I get a shooter that has serious problems with a tendency to slap the trigger the instant the sights cross the middle of the target, I hand them my 4" Smith 63 .22, and tell them, "The sights will NEVER stop wobbling - just keep them aligned in the zip code and press".
Smith and Ruger have both done 5-shot .357's (M60 or SP101) with 3-5" barrels and adjustable sights. Be where I'd start.