Fan clutch replacement guidance and recommendations

get yourself an infrared heat sensing gun (I got a cheap one at Harbor Freight that works just fine). You can check the temp at the thermostat housing by the temp gauge sensor at start up through fully warmed up and you can figure out actual temps at various gauge readings. It might be that you just need to recalibrate your perception of what the gauge readings really mean. Then you can search around with the gun for sources of heat in the engine compartment