You're on point with the revolver and pistol category thing...
Like most laws they didn't think it through - for the case of a wheelgun "upgrade" to pistol there could be a practical test to verify proficiency, which is probably at the root of the category thing; anybody can shoot a revolver but to be safe with a pistol you have to know the weapon.
Which of course breaks down in practical use because as a 1911 shooter and that's what I carry, I would need some instruction to be safe with any pistol that uses a decocker, for instance. Perhaps vice-versa for others. You can see how that (a proficiency test prior to re-issuance) would be complicated.
On the caliber, you must qualify with a centerfire - I think 9mm was the smallest round you could use - so you would not qual with a MkIII and then carry an Eagle (even if you could conceal one!).
Oh, and while I'm playing 'remove the foot from the mouth,' the course of fire is 50 rounds, 250 points scored on a standard B-27 silhouette.