OK, a couple of notes, because when we screw up we should learn as much as we can.
The internal aperture of the pump is a bit narrow, a few large grains might clog it. In fact, the corn thread only narrowed the aperture, husks then clogged it.
The top nut (furthest down when unit is upside down) requires manual dexterity to reinstall and can fall beneath the insulation. It's not entirely necessary as the pump bracket is threaded, but a nut rattling around in an appliance is dangerous, as any computer tech will tell you.
I hope my experience helps someone.