I gotta ask, who installed the tank and fittings?
A 3' loop in the pipe shouldn't be an issue as long as the loop isn't verticle and into the frost line where it would freeze.
The correct pressure for the tank with Constant Pressure System should be 70% of shut off pressure. So if your shut off is 60psi, you want 42 psi in the tank. To do that, shut off the pump and drain the tank then set your air pressure through the schrader valve.