Check your actual temperature at the thermostat housing with an infra-red sensor. It will be correct within a couple of degrees. If it is around 200 to 210 after warming up, your thermostat is working fine. If the engine temperature is where it should be turn the heatrr on full blast and check the two hoses going into the heater core at the firewall, one should be at operating temperature -- about 200 º the other about 10 - 15 degree cooler. If the cooler one is a lot cooler and no heat is present in the cab then you most likely have a blocked heater core and you will need to flush it. If both hoses are close to the operating temperature, you may have a problem with the blend door, or the heater core fins are plugged with duff.
How can you trust an atom, they make up everything