Erratic then no fuel pressure

Have a 2002 GC with a 4.0 L. Recently noticed a problem re-starting once it had been driven for a while and then sits for several hours. Plus there was a 'squeaking noise' near the tank that sounded almost like a pump oscillating on/off/on/off. Concerned the fuel pump was going bad, I changed two weeks ago. The noise is still there (maybe gone for a few days). Two days ago after driving two to three miles the Jeep lost power started missing and shut off. After sitting for a while it would restart but repeat this process. I changed the fuel pressure regulator/filter last night and drove around the block. Quit running half way. Finally was able to check the fuel pressure. Around 44 psi with key on - seems to hold but I did not leave in sitting very long. Started and at idle around 54 psi. After three to five minutes as the Jeep reached operating temperature the pressure gauge needle started vibrating very fast between approximately 50 - 55 psi. Soon after the gauge dropped to 40, 30, 20 then to around 0-5 psi, all in about ten seconds. Up until then the Jeep seemed to be running okay, maybe a little rougher idle, but soon after the pressure drop the idle became very rough on it shut off (as expected). Concerned I never really had a bad fuel pump but do now. Could there be something else causing the pump to essentially quit or drop pressure? As noted I changed the regulator/filter and the Jeep did the same thing. Thoughts?