Oh, I agree with you that it's his life and his choices. And you have written a lot of great tips about helping him shoot better.... whether the gun serves a purpose or not .. they make lots of different guns so we have choices.
All I'm saying is, maybe his expectations for a bobbed hammer snubby are more than they should be. I don't know what "shotgun patterns" mean to him. I'd like to see pictures of a target, both shot by him, and shot by someone else using the same gun.
Also I think he should keep in mind that gun "fit" is a real thing. With revolvers it may not be as nuanced as a sporting shotgun where people spend hundreds or thousands of dollars getting the right gun to fit their face and torso perfectly. But it could just be that his hand and that gun/grip combo are not and never will be a good combination.
I've had handguns that didn't "work" for me. Some I have learned how to make work after much practice as you describe. But my go-to gun is a single stack 9mm Walther PPS. My hand fits it perfectly. I could grab it quickly and I would naturally get a high grip every time. My trigger finger reach is perfect for great finger placement that allows me to fire without pulling the sights off target. I can pick it up and put nine shots on a small target very quickly every time.
Owning a handgun that doesn't fit him may be like being married to an abusive alcoholic. You can spend a lot of time "trying to make it work" but you may never be successful. And you may be wasting time and missing out on something that is naturally a perfect fit.