Vibration/noise issues after PTU replacement

Hello all-

The transfer case (PTU) on our 2012 CX-9 recently started dribbling gear oil on the driveway, so I replaced it myself.

What a nightmare. Twisted off exhaust studs, etc. Two-day project turned into 4 or 5 day ordeal.

Finally got the new PTU into place and everything buttoned up, torqued to specs.

Cranked the car and immediately discovered much more vibration/resonance at idle, especially in reverse. Made a test drive and experienced clunking noises like a driveshaft wobbling, vibration through floorboard, etc. at anything below 60mph. Interstate driving at 70-75 mph no issues whatsoever.

Got back under car and double-checked everything. All tight and "normal".

Assumed I must have damaged an engine mount in all the contortions to get the new PTU in place, so changed all three engine mounts, one at a time.

No improvement.

At this point I am a) afraid to get very far from home, b) sick of this car and it's designed in faults, c) totally clueless about how to proceed.

Does anyone have any ideas? And is there some black magic to "tuning" engine mounts so they are all pulling on the engine in a coordinated fashion?