Damn oil leak, Rear main??

Something that is SO FAR out there I have to mention it. I don’t think it is your problem. I have seen where the pilot hole on an aftermarket crank was drilled to deep and intersected the rod oil galley in the crank. There was a video, he would run the drill and build oil pressure and you could see the oil slowly start coming out of the pilot hole. Have to file that under “the last thing I would check!”