I would have someone new set up the ring and pinion. I have seen a lot of "Thats close enough" setups brake tons of parts. Sounds to me like not enough preload on the carrier or pinoin bearings or both. Something is moving around. My car has been 1.26 60' with a brake on a Dana 60,4.30 pro gears and stock caps and bolts @ 3170#. Never worn a gear or broke one. I would'nt give up on the Dana.
Bob