Don't overlook a revolver. You can't limp wrist them, no slide to rack, and bigger ammo for old fingers to manage. A .38 with whatever load he can handle is worth consideration. Size and weight should not be much of a concern if he isn't going to carry it. Even low-power wadcutters are wicked evil. More important than the gun he chooses would be to make sure he is safe with it.
Luckygunner did several articles on the .38 for defense. It's worth a look.
Oh, you might even consider taking him to a range, rent a gun or three, and let him shoot them first. Try before you buy. Hard to think of a down side to this and may prevent problems in the future. Old fingers (I got some) lose flexibility and strength with aging. If your father is still with us 10+ years from today, can he still use whatever solution you come up with. You might even find a used one at a reasonable price.
Luckygunner did several articles on the .38 for defense. It's worth a look.
Oh, you might even consider taking him to a range, rent a gun or three, and let him shoot them first. Try before you buy. Hard to think of a down side to this and may prevent problems in the future. Old fingers (I got some) lose flexibility and strength with aging. If your father is still with us 10+ years from today, can he still use whatever solution you come up with. You might even find a used one at a reasonable price.