So it turns out that no one really uses dosing pumps for continuous drip systems, because dosing pumps are designed to be precise and run intermittently. They are not at all designed to run continuously and if you insist on doing so they will die, often horrifically with smoke and melting plastic.
So after much soul searching and many, many pumps, I decided to go back to the drawing board. And by drawing board, I mean the nice folks over at KnowESys. They suggested that since my bucket system was inspired by the “WaterFarm” system, maybe I should take a cue from that system for the pump as well. Marc even showed me how to fashion an air-lift pump out of three types of rubber hose and a PVC pipe, and a few days later he sent me a new drip ring designed and 3D printed for me! He said he would publish the files, so I’ll post that in an update when he does.