sorry bout your cham dying. are you sure it died from dehydration. i have a dripper system, and mist once a day.
enclosure does sound bit big for a baby, i used a small fish tank first, then a exo terra 45x45x60, then when she was an adult upgraded to vivexotic ax36, with a little modifying for better airflow (replacing bits with mesh)
you sure he was eating fine, always best feeding by hand or hold a tub out for him so it can be monitered.
also was you dusting the food etc.
i use a ceramic bulb on a stat. but a household bulb can also be used as long as its on a stat and temps are good.