Not much air in the pump basket (maybe some tiny bubbles, not perfectly clear water, but certainly not lots of air) and we just cleaned the sand a couple of weeks ago by removing all of it and rinsing it one bucket load at a time in a wheelbarrow.Only way filter pressure goes down is your flowrate drops, suction side leak with lots of air, or there is channeling in the sand.
Yes and yes to the first question.Icy does your gauge drop to zero when the pump is off? Does it go right up as soon as the pump is primed and going good?
The dirt/sand-I almost always have something in my pool. I have lots of trees around as well as the cats that like to drink out of the pool and put their little paws in it