I repeat: replace the pump, even if it looks OK. You can get a brand new Melling or Enginequest pump from Rockauto for less than $40 delivered. I took a chance on an Enginequest pump when they were on clearance, it is the same casting as the Melling and is made in USA. High volume will run closer to $70.

It still sounds to me like the oil pump pressure relief valve is sticking open occasionally. This allows for the pump to be working which we know it is, as some times the pressure is where it's supposed to be. Then the engine speeds up to where the bypass opens and the little piston sticks. Now as you slow down the pump pumps less and the bypass is still open. Most of the oil from the pump goes right back into the sump.

On to checking bearings, I'll also repeat you should pull the #1 main and the #1 rod cap and look at the bearings and journals. If they are OK, the engine didn't suffer any permanent damage.

R.