The mix up was pounds/kilograms, not litres/gallons. The airline was changing its mass units, and fuel was calculated in kg but that number of pounds loaded. The problem was compounded by the flight being conducted (legally) with an inoperative Fuel Quantity Indicating System, and the drip-stick physical check of fuel tank levels was invalidated by the point at which the error in calculation was made.
Previous posts about the B767 RAT are correct; hyd output only, to a restricted part of only one hyd system (cannot remember which) and said by Boeing to be effective down to about 130 kt. With engines windmilling, there would have been some hyd output from the two Engine Driven Pumps on the L & R hyd systems. I have not seen any reports of the flight controls being heavy.