I'm sure you're good with the AX-15. That transmission will be supported for a lifetime.
The oscillating vibes is my problem too. And my swap resulted in gears that aren't deep enough (as you describe). IDK if you recall or not, but I initially started a thread on swapping the NSG-370 for the 32rh. That was a no-go for me for a number of reasons, so I went ahead with the 42rle. Now my issue is oscillating vibes come on at 73mph with 456 gears. If I regear to 513 they'll come on around 65mph. That's not really desirable. I know my answer is hubs, but that means selling my beadlocks, replacing them, re-gear, and the hubs. It's a hefty amount of change for 8mph. I think I'll retire mine as a DD in the near future, so it's not money I'm going to spend to solve them. I'm just going to enjoy my Jeep.
You might re-visit the thread I mentioned. Maybe you can figure it out. You're way smarter than me in this stuff.
EDIT: When I found the thread you'd already been there!
https://wranglertjforum.com/threads/nsg370-to-32rh-swap.73972/