I redesigned the extruder to reduce size a little. I also set the firmware to drive the extruder motor at 4031.5 steps per mm (32 rev / 1 in X 1 in / 25.4 mm X 200 steps / 1 rev X 16 microsteps /1 step = 4031.496 microsteps/mm).
The video shows the assembly running forward and reverse, then I feed in a piece of virgin filament and drive it forward (looks like I forgot to reverse it).
The nuts are still not centered very well but the machine manages to push the filament just fine anyway, so I will go ahead with print testing as-is. The offset in the nuts causes the whole frame to flex a little as the filament is driven- hopefully it won't tear itself apart.