A day or two after I had given up, I noticed my thermostat was setting itself according to the program I created. The variables just started matching. It was at this point that I made another interesting discovery: there is no way to disable Stringify without individually disabling all flows.
Since then I have witnessed a great many more janky spaghetti code behaviors. You always have to go back and check to be sure any values you set anywhere are what you saved them as in the flow. These values often either do not save or revert to defaults. The GPS trigger is laughably useless--delayed so long that I get back home and receive a notification that it has just noticed I left and set home=0. Tried checking my location every 15 minutes with timers this morning 3 miles away from my house, GPS radius of 1000ft, still thinks I'm home. Is there a simple thing to let me use my currently connected WIFI network to trigger a flow? Nope, I don't see one.