I agree with SpeedBump...
Start with that Whole House Filter and see what goes on when it is removed...
They are useless and most often the culprit for low pressure problems.
As far as the pre-charge on the pressure tank, that would be 2 psi less than the cut in pressure for the pump. The symptom of a problem there would be the pump short cycling. IE every time you run a small amount of water the pump turns on.
I'll leave you in SpeedBump's good hands now...
He's the guy I ask questions about well pump systems and water softeners...