To have oil gush out after such a short time, my thought is pressure build up in the oil pan. Has a critter plugged the oil pan vent? Might be worth a little investigation before pulling the oil pan.

There is another possible source for the oil I'd check before tearing too many things apart again.

I believe there is a plug in the rear end of the main oil gallery that is NOT a threaded plug.

If it's leaking, oil will be hitting the front side of the flywheel which will fling it everywhere.

You could pull the distributor, make a shaft with a screw driver type flat head (I ground a lag bolt head flat on both sides and trimmed it so to fit down the hole) you can put that on a drill. Put that down onto the oil pump groove that sets below the distributor. Run the drill and that will pump oil throughout the engine. I even put a rubber tube on the bolt so to not scratch the hole. That may be easier to work with than with a running engine. All that and with the help of a cell phone video, placed where you can't get an eye close to, you might be able record more specifically where the oil is coming from.