[postalbyke]

I hadn't thought this deeply before, but this is exactly why these guys say "SH3 is not a submarine simulator, rather, it is a game..."
okay!
you're in the control room, observe the dials above your helm/planes operators, they will show you the rpms of the engines (p+s), if you look to the right of all that jazz, you will find additional gauges that correspond to compressed air in tanks, co2 content of air, and furthest right (IIRC) will be your "forward and aft" battery charge indicators (fallacious because there was only one battery bank in a type II)
if you want to be sure that you are rigged for surface (and playing in english keyboard mode), press "s" for "surface" or "e" for "emergency surface (compressed air blow)"

also: if you want to know your propulsion lineup (battery recharge or full power) ask your chief engineer (the officer icons on the bottom of the screen) about propulsion, the appropriate mode will be highlighted (normal, battery charge, silent, snorkel). he can also tell you about compressed air, batteries, and CO2 content, as well as overall fuel level under "reports"
ummm... lemme reread your post :P
okay!
your crew and damage reports can be seen under "F7" or your appropriate crew/damage control button depending on which mod you are or aren't running. the "efficiency" bar will tell you how "awake" they are, less than one quarter, and believe them to be asleep at their post :P
sea state can be determined by analyzing the "weather report" which comes from the navigator, but for some reason i have to ask the surfaced conning officer for that report. there should be a shortcut key for that, also (rtfm(this is also my problem)). wind speed drives the sea state in this universe, so min of a couple m/s and the sea is glassy, and sea state... drowning... is 15m/s
your specific date and year is found (in the mod i'm running) by mousing over the "clock" in the bottom display of the screen.
period submerged is your dice, and can be analyzed by aforementioned gauges.
also in your court is the manner of improvements aboard your boat (you are the captain, you should know) and can be monitored in port under the "u-boat" screen on the right before going on mission.