Hi kyo... just trying to help here...
Regarding temperature, as Dr. Del mentioned, you can "eyeball" the temperature if you don't have a thermometer as follows:
Put your hand under your armpit. That should be around 97 degrees, unless you have a fever then it will be higher. So, when you feel right on the glass under the substrate, try to make it the same heat if not a little less than your armpit. So that, the top of your substrate should be a tad cooler than your armpit - around 92 degrees.
Now, I'm going to assume you have a thermostat for your house/room AC. Set that thermostat to 78. It would be better if your tank is not on the floor (I can't remember if you mentioned this) then your ambient temps in your snake's enclosure should be ok.
Hope this helps.