Yes, I'm using both channels on the same board - one for L and one for R. The + connects to IR and the - to IL, the ground channel is not populated on either board (shouldn't make a difference that I can see). The power supply is a single TREAD feeding both boards and I've checked the voltages at the various pins of both the OPAL/R and BUFL and BUFR positions and all seems well there.
Nope and I checked continuity across the pads to make the sure that the traces had not been cut.
I think I'm going to try jumping the pot out of the equation entirely and see what happens then. I have a source that can do digital attenuation so I shouldn't blow my fool head off. I would appreciate any suggestions for how to wire the input ground though (pin 1 on the XLRs), it's still unclear to me what the right connection here would be.