I can hold the top hose on mine without any nasty side affects other than a warm hand. You can test the thermostat in boiling water to see if it opens and closes.
You could remove the fan and leave it ticking over stood; if the gauge starts to creep up, take it for a drive and see if the air movement through the rad drops it again. If, whilst being stood for ages and the gauge doesn't move,
**** yourself and take it for a spin anyway to cool it down; heater on etc etc.

Mine has a muff fitted and the gauge only really gets excited on a good run and more so when working harder than normal ie. OD engaged.
'Fresh' coolant won't make the engine run hotter (it does what is says on the tin) but obviously is required as antifreeze............
Have you got an normal water pump or heavy duty one??