In addition to the 4 Engine driven pumps there are ADP's on systems 1 and 4 as they are heaviest users, AC motor pumps on 2 and 3 plus additional auxiliary ACMP on system 4 for braking when under tow/maint operations and as an option on system 1 for steering (these are powered by the ground handling bus though so will not be available in flight) slight drift from the original post I think but hopefully informative!
Each engine has an engine driven hydraulic pump, or EDP. Each hydraulic system has an Air Driven Pump, or ADP. Standard is one electric hydraulic pump, or ACP, on system 4, and many airplanes have a system 1 ACP, as well.
You're correct that the electric ACP pumps powered through the ground handling bus, and therefore not available in flight.
Systems 2 and 3 do not have standard electric hydraulic pumps.
160 KIAS is the minimum windmilling speed, and this is for hydraulics. It has nothing to do with electrical power. It also does not permit use of gear or flaps, hydraulically.