Coolant/Thermostat Problem???

[COBALT]

Ok, so I got all the new hoses on + a new thermostat, and started filling the system with coolant/water.

1. I thought these things took 15 or 16 quarts of coolant/water? I can only get 8 in. What's the scoop? The only way I know to get coolant in the system is to pull the cap on the flushing tee, and fill the radiator until crap comes out the tee, then run the truck while filling until you have fluid coming out of the tee AND the radiator is full...

2. The truck starts heating up damn quick. It goes past the 1st mark (where it normally sits all the time) and slowly creeps to the 1/2 way mark. This thing is heating up too fast I think. Isn't the thermostat supposed to open??? Is the thermostat not doing its job (it's in the right way), or is it simply that I don't have enough coolant in?

WTF?