Ah, double trouble

Yes, get a good thermostat as soon as you can. Rheostats are fine for stable temp rooms, but any fluctuations send the cage temps soaring. Sometimes the LOWEST setting on those things is still 100!

But very good to hear that you're tweaking and messing with things before the snake comes home!! Kudos!

So yes, get yourself a digital thermometer and a good t-stat and things should stabilize in no time.