Why not pump from well to house and skip the tank? Anyway, if the draw
from the tank is from the 2500 gal. mark, then you only have a 2500
gal. tank since you can't get the bottom 2500 gal. If you were to get a
shallow well jet pump and a 20 gal. pressure tank, the switch is
already on the pump and the 50ft. or so from the tank is nothing. The
weight of the water in the tank is probably equal to a booster pump.
Keep the pipe from the tank at least 1" in diameter with a check valve
just before the pump so you don't lose prime.