At a loss for words and ideas

[Googs]

I recently purchased a home with an appr. 22,000 gallon inground pool. I had learned that the pool had not been opened for 2+ seasons. When we took the cover off, it was an absolute disaster. Need new Liner and brickwork around the pool needs to be resurfaced.

I noticed my pool filter (DE filter - Hayward Perflex EC-75) never really had an abundance of pressure exuding from the jets (there are 2 jets and two skimmers on opposite sides of the pool), but the PSI gauge always read around the 5 - 15 mark.

Recently, the PSI gauge is reading no pressure. Now, it seems as if the PSI gauge is spiking (it goes from 2 PSI to 10 PSI and then back down resembling a metal detector when it finds a metal object). Meanwhile, I am getting very little suction from the skimmers on the pool deck (not even close enough to vacuum the pool) and the jets are pushing out tiny bubbles. I have backwashed it repeatedly, taken off the filter cover and cleaned the fingers, made sure the gasket on the skimmer within the filter's housing is properly fitted and checked to see if the impeller is obstructed, but I am still not getting no where near the PSI I need. In the skimmer (don't know the terminolgy that well) that is located within the filter's housing, there is some water entering it, but not nearly the amount I was getting a week or so ago.

My question is do I need:

(1) a new filter pump?
(2) a new filter altogether?
(3) or is this a pump blockage problem? If this is the case what are my alternatives (the guy at my local pool sotre said I may have air in the filter and I would have to "rip up your patio" to fix this problem.

Any help would be much appreciated as I really do not trust pool companies and their secret agendas - I don't mean to offend anyone but I have been taken to the cleaners by these guys before in the past