The reflex gages are the tall skinny glass sight glasses, yes? The back of the tube is bevelled so it reflects visibly when there is water. I think the pressure gage check valve would be to hold the highest impulse pressure so you got a chance to read it. You got me on the hole size, but it is tickling something like I've heard this before.
PS I was an FTG. On the Andrew Jackson I stood Torpedo Room watch and since it was 90 percent manual, the weekly weapons moves were all hands deals. There is something supremely macho about loading a torpedo tube by hand! Terry