I understand the correct pressure is nearer to 40psig?

I guess there is a flexible segment somewhere in the return line. If too much fuel is returning (i.e. the regulated pressure is too low), then pinching the return line would raise the pressure (since the pump can supply a lot extra if it is good). If the regulator is ok but the pump is not supplying enough pressure then pinching the return line wouldn't help you since little or no fuel would be returning.

If the pressure from the pump is too low, is it possible the tank intake hose or screen is blocked with dirt?

I had a 164 with dirt in the tank, a weak fuel pump, and a stuck regulator (pressure too high). The car ran ok except it sometimes died on hills (dirt sloshed around in the tank and blocked the intake). Not knowing why, I replaced the fuel pump - then the car wouldn't run right at all because the mixture was far too rich with lots black smoke out the exhaust (new pump - high pressure). Replacing the regulator too cured the rich running. Replacing the tank and inlet sleeve cured the intermittent stall. Evidently when I first got the car the stuck regulator and weak fuel pump balanced each other pretty well.