1. I read that every time I order my crew to the deck gun my watch officer loses moral. Is this true?
Of course not...
2. I also read that if I load a game save that I initiated that also affects moral. Is this true?
I never noticed that. Where did you read that?
3. Can my crew gain experience by carrying out drill crash dives, etc?
Not really...
4. If I switch off one engine on the surface can I still recharge my batteries?
5. Does switching to one engine save much fuel?
Engine/shafts selector is mostly just a demonstration of TDW's modding abilities. There isn't much use of it in normal gameplay...