Matt Beckwith,
having gone as far as you have I would not say that diving is not in your future. I will say that I gleaned enough to make me agree that private instruction may be a good way to go.
The concerns about drowning are rational enough but they should be under control before getting in the after with a regulator. i did not get a sense of your general level of comfort in the water. Swimming, snorkeling? If being in and on the water has someone uneasy scuba will be trough sledding. I dis not see any mention of in the water
skin-diving as part of confined or open water. I consider this essential, especially to someone who is not a natural.
If you ended up paying for the shop's classroom instruction I wish you had gone, even if seemed redundant. That is where bonding starts and you get some understanding of the local experience. You obviously got the academic content but may have missed some of the fun.
i agree that empty lung regulator recovery should be taught. You knew how to recover and how to purge but had not connected the dots.
With regard to clearing our mask, remember that you will not have the luxury of catching your breath before it may someday get knocked off your face. The good news is that water up the schnoz and other discomforts fade with experience so just deal with it.
Equalization can be practiced topside and is an acquired skill. Start doing it 1 or 2 times a day while plotting your next move. Sneaking up on your ears with just enough pressure is the idea. Too much and the tube slam shut. I'm sure you know the rest as a doctor. When you dove do it on the drive over, as you don your gear, get in the water and just before submerging. Then plan on doing it with each breath during descent. Once you get a sense of things you can modify the routine.
The cylinder was probably closer to 37 pounds to make you feel better.
Claustrophobia should not have been a surprise. they should have had you in hood 7 gloves after the first night.
"Don't worry, you have air" is not a flip response. It's a fundamental circuit breaker to panic, a real killer. It may not have been the best poolside manner but take it to heart. As long as you are breathing anything else is just an inconvenience.
With regard to fitness and the site a few thoughts come to mind. Handling gear is something of a dance. The first times are difficult. It will get easier with experience. Too many macho instructors with that experience have poor consideration for what may work better for some. I know plenty of divers that for various reasons prefer to stage and don the heavy gear near the water and exit similarly. Doing so is surely an option.
Keep an eye on heat stress. That probably was at the root of the stress heading downhill to the water and it would exacerbate the claustrophobia. Pour a liter of water into your suit to act as a heat sink. Warm the water
if the conditions are cooler.
As for cardio fitness you are better qualified than I but plenty of young apparently fit divers end their early dive days whooped. Learning to pace yourself is a big part of it, especially on exit. Spend a few minutes in the shallows, upright with your BC still carrying most of the weight. let you body re-acclimate to 1G before exiting in measured steps. I'm 4 years younger, not especially fit, dive lots of hilly sites but rarely pause while exiting. I'm not usually the 1st back to the car either!
So if this is something that you and your wife want to add to your lives together do your homework and go find an instructor that you would count as a friend, set-up a private course and re-start the journey. Everything I read in your quarry experience says you can do this.
Pete