Perhaps it was the mention of the relief springs retention plug in the pump being installed backwards? Or the relief valve it self being stuck. The plug should be with the cup side facing INTO the pump, not facing out. Blockage was mentioned in regards to the small rocker holes being blocked and raising shaft pressure.
If you DO have a Melling then maybe you should hold on a bit before pulling. Per KK's data, I would expect either the standard or HV Melling to produce 10-15 psi higher than the non-Melling pump, at least at the 1500 rpm or so and higher. You are not far from that. I surely would not pull the motor before checking the rockers thoroughly to see if you could get that leakage settled down, and checking with another pressure gauge.
BTW, did you ever get a video of the oil form the rockers? We are blind on this end to what is really going on.