After a couple days of banging my head against the wall, it works! I was referencing just the wrong memory for the send command, I also made use of @lukecyca’s awesome debounce library providing a queue of debounced button presses:
Here’s me showing that it works (I threw the battery on there to show there’s no trickery through cables).
My circuit board for the ADC should arrive on Tuesday, and I’ll need to now get out the old breadboard to start roughing out a circuit. This is exciting!