When draining a water heater, open a few hot water taps for air, in addition to the T&P valve. It should drain much faster. (Turn off the power to it first, of course.)
If your pump is set at 40-60 psi cut-on/cut-off, the pressure tank should be two psi below the cut-on, or at 38 psi. With the pump off and the water pressure all drained off, check the tank again with a tire pressure gauge. Your's should be 38 psi. If it needs air, then air it up to that with a bicycle pump or portable air tank or compressor.
Usually, hot water pressure should be about equal to the cold water pressure going into the tank. Make certain that the cold water supply valve to it is wide open. If it seems to be, and the hot water pressure is still too low, I would turn off the pump and take that valve apart to check it and clean any build-up or debris from it first.
If that valve is O.K., then there may be water heater debris clogging the hot water side of the various facuets, and you may have to take each apart to clear it.