Hello, andto BP.net.
Make sure that the probe for the Repti-Temp 500 is mounted between the Under Tank Heater and the glass. I would suggest using a $10 Lutron lamp dimmer from Home Depot or Lowes to regulate the heat emmitter. Here is the link to a thread with photos of one:
http://ball-pythons.net/forums/showt...t-Instructions
I suspect part of the problem with the cool side temps is that it is caused by your house a/c. You could try setting your home thermostat to 75-77F. Another suggestion that you can try is adding something to the back and two ends to help insulate the tank a little. Colored foam board, available at Target and Wal-Mart in the school supplies section near the poster board, will look the best, but, you can also use pieces of cardboard.
For the humidity, you could try covering the screen top with aluminum foil or a piece of plexiglass, except where the CHE is. You might also try a larger water bowl, if possible.