Very insightful write up Niznai, greatly appreciated!
My diff never leaked out of the outdrives, I'm using the red o-rings from the kit and a very little amount of 100K diff oil for sealing instead of grease/slime. Stock 900# Tamiya oil in the diff. Where the diff halves meet, some oil escaped and lightly coated the pulley. I have cleaned it as much as possible and re tightened the screws as evenly as possible. Doesn't look like any more oil has leaked out but it is hard to tell when there is already a light coating on the pulley from before. I guess I will know for sure when I receive my new esc so I can run the car.