When is coolant temp too hot. About 216

You could drive yourself crazy trying to find the "correct" place for a sender unit. Engine temp is a relative measurement. Just an average so to speak. No matter where the sender is placed there will be a different reading somewhere else. The infrared thermometers only measure surface temp so that reading will be cooler than the internal temp. Bottom line: install a known good sender/gauge
whether stock or aftermarket. Use a known good thermostat. (test it in a pan of water on the stove with a good cooking thermometer). I prefer 180 degree in my climate. Make sure your radiator and cooling system is clean inside and out. Use a 50/50 mix of engine coolant, and make sure your cooling fan works properly. (if you have a clutch type fan). It sounds like your engine just runs warm and is not overheating. tmm