Get the water bowl off the heat pad - you're encouraging bacterial growth in the warm water and it's not helping your humidity level enough to be worth it.
Also, do as Melindaste suggested and get the lil humidity gauge, but I think you'll find the humidity isn't quite as bad as it might seem, especially if you cover at least half the screen. I live in the desert and just with half the screen lid covered, reasonable sized waterbowl, and paper towel for substrate, I had 50% humidity. Heat lights are far, far worse than heat pads for drying the air out.
The gauge will definately help you out though. I don't keep one in my tubs 100% of the time but when the weather's been dry or if someone's going into shed I'll stick a guage in the tub to keep an eye on things. Helps a lot 
Good luck!
~jenny
-----
"The python has, and I fib no fibs,
318 pairs of ribs.
In stating this I place reliance
On a seance with one who died for science
This figure is sworn to and attested,
He counted them while being digested."
~Ogden Nash
jenny.thegreenes.org
"If you're happy and you know it,
Bomb Iraq!
If you cannot find Osama,
Bomb Iraq!
If the terrorists are frisky,
Pakistan is looking shifty,
North Korea is too risky,
Bomb Iraq!
