When the system is in use, the pump SHOULD NEVER reach cut out pressure. So it is working FINE now, and it wasn’t working fine at 30/50 because the pump was cycling on and off while “in use”. Cycling on and off is the worst thing you can do to a pump.
As long as it reaches cut out pressure after the sprinklers go off, your good. And a J7S should be able to make 70 PSI, so 40/60 should be fine.
It kills me that people think a pump should be “cycling properly” when using water. There is no such thing as “proper cycling”. It is not a good thing for the pump to cycle at all while water is being used. Pumps are made to run “continuously”, and will last much longer for doing so. Cycling on and off is what kills pumps.