I've been struggling with my Pumptrol (Square D 9013FSQ 2) pressure switch for hours, and fails to solve my pressure issue.

It had somehow drifted, and was kicking in at 15 lbs (way too low) and off at 70 lbs (way too high). I'm aiming for 40-60, so I turned the small nut counter-clockwise and the larger nut clockwise. I have been able to raise the cut-on pressure to 40, but now cut-off is at 78 lbs (!! ). I would have guessed that turning the small nut counter-clockwise would let me reduce cut-off pressure, but that small nut has been turned ccw almost as far as it can go (it's almost off the bolt!), and the spring underneath is loose, not even touching the nut.

Is my pressure switch faulty? Or am I missing the point?

The large nut adjusts both cut in and cut out pressures up or down. Clockwise goes up, counterclockwise goes down. The small nut only adjusts cut out pressure. However, with a 55# differential between cutout and cutin, it makes me suspect the little pipe leading to your switch is clogged with crud. I'd check that.

You can try to lower the 70# cutout with the small nut by turning it counterclockwise. You want a 20# or so differential between cutin/cutout.

First you adjust the nut on the long spring ( the range nut ) to get the right cut on/in pressure ( u wanted 40 psi) Clockwise raises the pressure.

Once that is set turn the nut on the short spring ( the differential nut) to adjust the cut off/out (60 psi) pressure, Clockwise to increase.

They MUST be done in this order.