Wow... did he name the car Exxon Valdez
First, the hole in the flywheel housing is mildly concerning, not related to the leak but concerning none the less.
There is no real seal in the modern sense, the oil that makes it to the back of the bearing should get caught in the slinger and then funneled back to the sump. Wear in the rear main will let more oil through and will overwhelm the slinger and just slip right past and onto the ground.
Did you check the oil level on the dip stick?
Did you check the breather cap for an obstruction?
How does the engine run otherwise? Is there a noticeable amount of end play? On my old engine there was about 1/16" and it only left a few drops. For reference I believe the max. tolerance specified is .006".