For the deck gun I use the F5 to get them OUT of the gun really. Use the binocs to pick a target and fire at it, they'll automatically get on the gun. Press F5 twice to get them off the gun. (First time brings up the 'gun active' icon, even though they are, second one takes them off.)
To load the external torpedoes, in rough seas or even submerged, just press H, then Torpedoes then drag them from the External area to the Reserves area just below it. 30 seconds later it'll move down into the boat and start to load in a tube if available. This is with "realistic reload times" checked...
__________________
|