Just dropped the gauge and thank you did not know that, and I read on here some where that 18 inches is where you might want it. Yes no??I have a couple suggestions if you don't mine. The temp/humidity gauge is too high, should be tort level. It's always going to be warmer and more humid the higher the gauge is. Also, he sure the UVB is not too high or it won't be beneficial. The bulbs info usually will tell you the min and max distance. In the pic the light and che look quite high to be beneficial at tort level.
About 80 each, I'm happyIt's been awhile, but I think it's anywhere between 12-24 inches, so your 18 would be fine as long as that gets the temps under it you want.