Oil pressure drops at Idle also sputter/knocking when accelerating

First the Express has been sitting for 2 years prior to me buying it a month ago.

It was driven less that 2,500 miles a year.

I have put about 1,300 miles on it since buying it.

Since buying the van I have
- replaced transmission cooler - upgraded - the cooler and lines were leaking
- replaced oil pressure sensor
- Had a new oil pump put in
- new oil change (went full syn) and filter
- just today, installed new spark plugs, cables, and ignition coil module

So first we have the issue with the oil pressure - when the van warms up the pressure drops low (5-15 psi) when at idle or low cruising speeds sub 30 - check gauge lights comes on and off based on speed. At a stopped idle it goes to 0-5 psi.

The oil pump and oil pressure sensor have been replaced and it's still happening. Should I be concerned of oil starvation still or that the gauge is bad? I had been driving it all around town for a few weeks with no problems ran solid.

Last Friday I had the oil pump replaced after driving 6 hours from Ohio to North Carolina. - And about 2-3 of those hours the Service engine soon light was blinking on and off for pretty much the entire period at the end.

In addition, towards the end of the trip, I started feeling the sputtering sounds when accelerating - a significant loss of power and acceleration.

I'm concerned the gauge was showing bad pressure and I was driving the vehicle with oil starvation and caused damage internally to the engine?

Today I replaced the spark plugs, cables and ignition coil module. The Service engine light wasn't blinking but I also didn't drive it that much because I am still getting the sound and feeling when accelerating.

I have to travel north to WV then back to Ohio.

Should I continue to drive the vehicle? What else could it be?