Need more pressure to showers and faucets psi gauge setting on 20 psi, How many turns per nut do I need to turn them and do I need to tighten or loosen?

Tighten the large, center nut only. Turn it clockwise. It is somewhat trial and error. Try a full turn and test the system to see what that did for you. Keep at it until you get what you want. However, I think you might be misreading your gauge. I can't imagine a switch that turns the pump off at 20# UNLESS someone before you adjusted it down radically. Be sure that 20# is where the pump is cutting off. Also, be sure your gauge is accurate. You can check the pressure at the air valve at the top of the tank. It should be about the same as the gauge.