Somebody yesterday on the SH4 Mods forum posted this link:
US NAVY TORPEDOES, by Frederick J Milford, Part Two: The great torpedo scandal, 1941-43.
As it says, historically both exploder types and the depth mechanism were messed up untill later in the war.
So the question is if these are bugs imitating reality or reality imitating buigs? :p
As far as the exploder switch not keeping its position between switch screens or torps, this is definitely a bug. In SH3, the equivalent switch retained its position. But both games suffer also from the torpedo settings not being saved between game sessions, which is a pity.