Just replaced the waterpump and timing belt, bent exhaust valves and head gasket and thermostat. Car runs again but still overheating!

99 Jetta 2.0L, w/AEG engine, automatic.

The new waterpump has a metal impeller, old one had a plastic one. Car warms up and gauge goes to 190degrees after car runs for awhile and then car shuts off (I'm assuming because computer sensed a max temp for engine?) Anyways, what gives here? I did add about a gallon of antifreeze and I see no leaks.

The upper radiator hose is hot but the lower one, which comes from the thermostat is basically cold - not even warm.

I also changed out the thermostat while replacing the waterpump and I installed it the right way - spring side toward engine.

I did open the drain at the lower hose - coolant comes out fast then slows way down. Each time I do this it repeats - fast then slow to a trickle. Is there a valve somewhere else to purge air out of the system?

As I said, the water pump is new w/metal impeller. Before I installed the timing belt I turned it and it spun w/out any resistance.

Would a stuck thermostat prevent coolant from circulating in this car?