Heres another way of playing SH3 at 100% realism. Install the following mods if you haven't.
Rub1.45 - makes those 100,000 tonnage scores and finding convoys much harder. Also dont know if its the mod or 1.4 patch but destroyers are more cunning.
WAW realism - no map updates
SH3 Commander - for the very long reload time of your deck gun
or have no deckgun altogether.
Ive played like this for months but just for a change im going back to the stock game with a few graphic/sound mods as my only extras.