I think you have the right idea with the 38 or 9mm. The nice thing about the .38 revolver is that it won't jam, the 9mm I think you should learn something about taking immediate action and good maintenance is always important. There is a reason some cops like the .44, it's because it's a revolver so it won't jam and it's a hand cannon, that's a lot of firepower so I think that one would be ill-advised. What I get from the thread is your familiar with weapons and have a good idea what is meant by muzzle awareness and the various gun safety that is so much a part of gun ownership.
Just one thing, according to Army doctrine the muscle memory of raise, safety catch, fire, safety takes some 5,000 repetitions to make it automatic. I believe in responsible gun ownership but the first rule is safety first. I know that sounds preachy but I've known a few guys who had accidents cleaning the stupid thing so, just a word to the wise.
By the way, the muzzle is notoriously hard to control, off a fraction here, it's way off down range. A hand gun is for close range and cops miss about 4 in 5 shots, do take note. If you have to use it you will be excited, it's not the range and things can be very confusing. Know what is going on with that weapon before you send that bullet down range because you can't get it back.
You want to check that weapon every time you pick it up, make sure it's clear and do a function check. That trigger finger should go right to the safety catch. Don't trust it over 30 feet in range, I'm not kidding, it's real easy to be off a little and have a bullet going on it's journey to who knows where.
Other then that you have a good head on your shoulders, if all else fails, take all instructions from the tower. Just a few words of advice, I sincerely hope you never have to use it but as long as it's in your possession take good care and I'm sure you will be fine.
Grace and peace,
Mark