1. Yes. At least to the best of current modding ability.
2. I don't really count on torpedo depth to be really fixed until 43. They knew it was a problem and the main "fix" wa to set them to run shallow. This works in-game as well.
3. Never count on the Mark VI. The magnetic exploder was never fixed. It was just deactivated and shelved. It was all contact after problems were solved.
4. The Mark 23's were really just modified Mark 14s. As you said--the difference was they only had high speed setting. I've never talked to a submariner that differentiated between the 2 (they always refer to any steam as Mark 14). I can't say for certain about in game (I always carry 14's or 18's) but in RL, the 14's and 23's were identical except for speed.
You may also read that the torpedo fixes came faster in Pearl than they did in Australia. Adm Christie in Australia had his name attached to the Mark VI exploder and refused to admit it didn't work--even after problems were proved. He continued to order the Magnetic exploder to be used right up to 1944. (this command difference is not modelled in-game. would be a serious PITA). Most skippers just deactivated them when they went on patrol and fudged their reports.
Hope that helps!
Happy New Year!!!
