After the lack of success using constant current drivers, we continued to search for a driver that would be cost effective, off the shelf and easy to implement. The UNL2003AN is a common driver circuit used in small stepper motor drivers.
We won't need the entire circuit, but the ULN2003 circuit, which is a Darlington Transistor Array: ULN200x, ULQ200x High-Voltage, High-Current Darlington Transistor Arrays datasheet (Rev. P) (ti.com)
Wiring this up to my prototype rig and it really works. It is simpler and more responsive than my initial level shifter rig, and adds the driver protections I need to protect the controller. So far so good. I'll continue to build out and test with this circuit and see how everything works.