As mike mentioned about the cap needing to hold pressure, you need a new cap. (BTW the new cap might uncover all kinds of issues. Like leaks etc. When the cap doesn't hold pressure you can have a gaping hole somewhere and not have a leak but once you apply pressure it will leak for sure. Not saying it will happen, Just be ready)
When it started going a little high the fuel gage was working, then when going to lunch the fuel gage stopped working. It’s done that before but never overheated
My point is that the reliability of your dash temp guages is suspect. I would at least temporarily invest in a aftermarket under dash temp guage to know what is really going on. Then after you have sorted out the engine and if it is indeed overheating, work on the gauge cluster.
General rule of thumb... If you can hold your bare hand on a surface it is generally less than 120 deg F. After 3 hours I doubt that there is a surface, or coolant that is greater than 120. After 3 hours and the dash temp guages goes up to anything more than the right most normal line ( I would expect it to be way less than that) you guages or sender or wiring or ivr or printed cir board in the cluster is failing.
I drive my dart for about 30 minutes 1 hour and 45 minutes ago. I just went out and with a thermal temp guages measured the hotest to be 145F, I could touch every part of the engine.