Only after breadboarding the control circuit did I realize that the thermal control circuit was way too complex. I thought I needed a virtual ground so my error signal could be positive or negative, however, I don't actually care if the unit is too hot. If the temperature is too hot there is nothing I can do. I've revised the circuit so that a low temperature creates a positive error signal and anything higher than the setpoint is zero.

The topology is fundamentally the same as last time, minus the virtual ground headaches.