My pinion nut removal tool arrived today, so I finally got the differential broken the rest of the way down. I ended up having to use the big rattle gun for 2 solid minutes to get that thing backed out. Those aluminum threads were tore up pretty badly by the time I was finished.
I cup wheeled the threads and not most of the damaged stuff more or less okay. The steel nut, unsurprisingly, was in perfect condition.
I then had to weld in a bolt to try to extract the small pinion bearing that was beat so badly that I would swear it was originally a bushing.
The bolt, combined with a GM body bushing washer worked perfectly to pull the bearing out, at least until the bearing broke in the middle.
Since I didn't have the forethought to buy a second bolt, I had to grind the bearing and the weld off of the bolt, then try again. Once I finally got it all out, I pounded the big bearing off of the pinion, cleaned the water that was still trapped between the big bearing and the pinion, and wire wheeled and sanded the rather beat up end that interfaces the small bearing.
I got it fairly smooth but since it's a needle bearing, if it fails again that will be the likely failure point. I pounded the pinion assembly into place, then liberally greased the threads on that pinion nut, and screwed the nut back down. Lucky it went down all the way with only a ratchet, but I wouldn't recommend pulling it apart again. Ever.
Once the wife goes to bed, I will silicone the halves together and reinstall it back in the bike.