[Accelo]

I helped a gal with her Z28 / IROC Camaro. Kept breaking the flex plate. I just kept installing new one. Finally got the OK to check the run-out . I reinstalled the transmission, without the converter. Just used a dial indicator, on the flex plate and indicator on the transmission, to inspect the run-out . Using the front pump machined surface I found it had .100 axial run-out in 10" diameter circle. Back of the block or the front of the transmission wasn't machined correctly. I put it back together and informed the customer of the issue. Never saw the Camaro again.
My point is the pump can take a horrendous amount of run-out and the bushing and pump lived.

You didn't mention your max rpm. Could it be ballooning? Crankshaft axial run-out?
You have covered all the major points. Time to replace the converter. I was wondering why it wasn't replaced when the pump failed the first time, or did I miss something? No way to keep the debris out the converter when the pump fails internally.