EDIT: Ok, so this is getting incredibly frustrating. I just dialed in new values to compensate for the discrepancy and suddenly the result is halved again. Went up to 55000 on Add Force and 18000 on torque. Worked ok for about five minutes and then it's like the object suddenly weighs 100 times more. WTF Unreal?
EDIT 2: Perhaps I should have posed this more like -- has anyone noticed how the add force and add torque functions are inconsistent? Is it just me?