I'm just now going through the same thing, but I'm probably a few months ahead of you. I took CCW training and discussed this with the instructor. His advice was to plan on 2 guns: initially a good .22 for training and practice, and then the for real carry gun. I purchased a new Ruger Single Six in .22LR/.22WMR and use it for practice. It allows me to work on technique because of low noise/recoil and the cheap ammo isn't a bad thing either. So far I've put 1500 rounds through it and feel that I'm finally getting the technique down as my groups are fairly tight and consistent. I shoot 100-150 rounds at each of 7 and 25 yards each time out and gon't get fatigued or broke doing it.
I'm now into shopping for the carry gun. I do not intend to use the .22 for carry, even though it has .22WMR capability. Your grandfather is right if you're good enough for an eyeball shot in a combat situation, but as a practical matter the only way a .22 will stop someone intent on doing GBH (great bodily harm) is if you have time to empty it and you're shooting .22 mag hollow points, IMHO.
The choice of caliber for the carry gun pretty much boils down to how good a shot you are, and I don't think I'm that good, especially under attack. As for noise, that can actually be an advantage in that situation, so unlike you, I WANT a loud carry gun. There's lots of debate about the best round for a one shot stop, and I've decided to go with .357 mag as that's how I interpret the data. Frankly, one good hit with anything from .38 Spec +P through .44 mag, including .40 s&W, .357 mag, 9mm, etc. should give you enough time for a second killing shot if needed, so there really is no one single magic bullet. I think the .357 mag has good credentials as far as doing damage to an attacker, and I can afford to practice, both in terms of dollars and effect on the old body, with it using cheaper ammo than the combat stuff.
Anyway, that's my opinion. Now, what that's all lead me to is trying to find the "right" .357 - one that fits my hand and can also carry without printing. There are lots and lots of candidates, but so far it's Ruger's SP101 (KXP321XL), S&W's Model 649 or a Taurus 850 or 851. Gotta get my hands on some and bust some caps before I make my final decision, however.