1.You should have two hides, one on the hot side and one on the cool side. They should be identical and small enough to make the snake feel secure. The snake should be able to touch all sides of the hide. You may want to get 2 of the medium sized Exo Terra caves, it looks like you have a large in the picture.
2. From your picture, it looks like the heat lamp is located far away from the tank?? If it is one of those clamp-lamp type fixtures, try to set the fixture directly on the screen, that way you aren't losing so much heat between the tank and the bulb.
The ground temp should be between 90 and 92 on the hot side. It looks like you have a thermometer with a probe, but I don't see from the pictures where it is located. I tape the probe to the glass under the hot side hide. This is where it should get teh 90-92 degree reading. The ambient (air) temperature on the cool side should not fall below 80 degrees. What kind of heat mat are you using? If it is one designed for reptiles (ex: zoomed, kritterz), you should be using a thermostat or a dimmer switch to control the temperature so that you don't run the risk of your snake getting thermal burns. If you are using a heat pad meant for people, go out and buy one that is designed for reptiles. If the ground temp isn't above 80, even with the heat lamp on it, try using a higher wattage bulb.
I have to make one more plug to get a thermostat. Constant temps are essential for a happy and healthy BP and proportional thermostats are the most reliable way to do that.
3. You need to raise the humidity asap. That along with low temps will lead to respitory infections. To do this, try taping off the majority of the screen lid. Here is a link explaining how to do this:
http://www.ball-pythons.net/forums/s...ad.php?t=32800
Also, you can try to switch to a coconut husk substrate (Bed-a-Beast, Eco Earth, etc..). It tends to hold humidity better. Aside from trying those two things, you can mist a few times a day.
Hope this is helpful. Good luck with your setup!