Q: Enging not reaching operating temperature and heater not getting hot

I can plug in my block heater at night on nights it reaches around 20 degrees outstide. On my programmer screen it shows engine temp at 130 degree when i turn it on. When i unplug the cord from the block heater while the truck is running, the temperature drops rapidly. Sitting at idle it will drop back into the 80's. I drive 30 minutes on the highway at 78mph to work and the engine temperature never got over 120-130 degrees and my heater never gets hot (mildy warm). When i come to a stop in town after the 30 minute drive i can watch my engine temp drop fairly quickly to 110. While it is ~20 degrees outside, I feel the engine should still stay within operating range around 200 degrees and my heater should be blowing hot air by then. My suspicion is a stuck thermostat. Can you provide insight to this issue? In the hotter days, the engine temp will climb over 200 and heater will get much warmer.

My car has 205000 miles.
My car has an automatic transmission.