Thats a better explanation. As said, check your heater core, if its leaking you will smell hot coolant with the climate control on hot and the fan on.
Also, maybe faulty rad cap.
I would go back to a normal temp thermostat, they're not that expensive genuine, and I can't see there being any benefits of a colder one for normal driving.

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F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i