Also might be worth mentioning that the Infared bulb will lower your humidity considerably. You won't be able to see for yourself until you get a digital hygrometer.
Is the thermostat probe INSIDE the enclosure? if so, I would recommend moving it to the outside and tape it directly to the heat mat. That way the snake can't move it or pee on it or mess it up and give the thermostat a false reading, which would cause the heat mat to overheat.
Wouldn't the probe being outside on the mat cause it to be too cold? The heat goes up, probe would be on bottom. Also I use mulch for substrate and it has to have heat loss there.