Found it.
I edited the GameplaySettings.cfg, (obviously!)
In it you'll find a block of text for each difficulty setting.
Looks something like this
[Realistic]
LimitedBatteries=true
LimitedCompressedAir=true
LimitedO2=true
LimitedFuel=true
RealisticRepairTime=true
ManualTargetingSystem=true
NoMapUpdate=false
RealisticSensors=true
DudTorpedoes=true
RealisticReload=true
NoEventCamera=true
NoExternalView=false
NoStabilizeView=false
MPShowPlayerNames=true
MPShowTorpedoes=true
NoShipHealthBar=true
NoGunProjectilePath=true
Edit each value to whatever you want.
Seems to be the only way of turning individual realism options on or off when starting a career.
Unless I missed something
