lol
Mini update:
I added some more in-boost timing the other day and the Jeep was really pulling hard. The rear end was squatting hard while accelerating (still on ~6.5psi) and was starting to get some slingshot feel to it. Then I started hearing a ticking which very quickly turned into a full blown pneumatic jackhammering sound. It drove completely fine but just made a hellacious knocking sound. The sound didn't happen in 4th gear or when the clutch was pressed in, so it sounds to me like a dead giveaway that it's a countershaft bearing failure, or possibly but less likely a broken tooth. The transmission has always dripped so I wonder if it just got low and died coincidentally while I was playing with the turbo.
Anyway I'll pull it soon and see what's going on. If no parts are broken I'll just rebuild it for a little over $100. Otherwise I'll have to find another AX-5 transmission (from a wrangler or cherokee) to swap in and be on transmission #4 (probably need a spare trans anyway).
If you have an AX-5 trans you can sell, let me know.