Cute corn there! And nice setup.
Do you have a UTH or are you just using the heat lamp? If you are just using the heatlamp, then I probably wouldn't shut it off, just keep an eye on the temps, and use a thermostat with the lamp. But from my experience, I use a UTH with my corn's tank and it has been great at keeping the temps perfect.
As far as a temp/humidity gauge I would go with an accurite, they are found at most walmarts and I think I read on here that someone found one at a Lowes. The kind that I have reads two temps (one from the base unit and one from a probe) and also reads the humidity as well. I use them in all of my snake enclosures and they have been wonderful!!
And as far as humidity, mine has been doing fine with the ambient humidity in my house (which usually is around 40 - 45% near the snake enclosures). If I notice that he is going into shed, I try to bump up humidity for him a little, but I have noticed that even in the ambient humidity he still sheds perfectly. So if your humidity is off by a little for a short while then I wouldn't really worry about it. Looking again at the caresheet for corns on this site, it doesn't even list a specific humidity other than just the ambient humidity of the home it lives in.
Hope this helps and good luck with your new little cutie!!
Man I guess I just type too slow!!