For the crush depths for each boat, I believe all you need to do is to check the depth dial gauge and see where the "red warning needle" is set. That should be the "guaranteed" depth from the manufacturer of the boat.
Typically, you should be good for something beyond the depth. Just how much deeper you can go without "issues" is something that you will need to test for yourself. With time compression obviously off, and in deep waters; try going to the manufacturers "test" depth and then gradually go deeper- I usually increase the depth in increments of 5-10 feet until I lose my nerve, or I start getting leaks or warnings from the crew.
Keep a close eye on your depth gauge and begin your assent at the first sign of problems. Now subtract 25 feet from that depth and that is what I use for my personal "crush depth" - also remember that ANY hull damage will reduce the maximum depth that you can go. If I have 10% hull damage, I will reduce my "crush depth" by 10% as well.
If you happen to "die" during the test- just reload your last save and consider your new found knowledge of your boat as command clairvoyance!
