I remember both mods.

The crush depth program was developed to correct Stock SH3 issues. It's now been taken care of, no need for the separate proggy.
Firstly, GWX has (as near as possible) accurate Crush Depths but as Tango says, SH3 Commander can randomise this for you. FYI, in GWX you can go a lot deeper than the guage allows for but be careful.
The 400m depth gauge. As the XXI historically was the only UBoat rated anywhere near that depth, it's the only boat that should have it. The type 2, 7 & 9s should keep their current guages. Besides, where's the fun in knowing when your boat is going to implode.