Glass tanks are a challenge for keeping humidity up. Wet towels are a bad idea, it just breeds bacteria and mold, and you really don't want that in your tank. Try to lose the heat lamps if you can, as they suck humidity OUT of your enclosure. Stick with heat pads, and a larger water bowl.

Tubs are also a great way to easily maintain heat and humidity. Not as pretty as tanks, but much easier to maintain.