[Wgesnerjr]

Just thinkin.
Have You looked at thermostat? I can't remember if you have tested its operation in the pot of water. Specifically does it open, at what temp and if does; all the way? even if it's new, it might be defective.

Another thought, why not use a lower temp thermostat. Being that I live in HOTlanta, we regularly use a 160 thermostat since our summer days can be over 100 degrees for weeks in the summer. Our winters are usually mild and have not suffered from not enough heat.

Again, just thinkin.