The Best thing you could do for the dehydration is to get to a petstore and get a product (Not usually expensive) called JUMPSTART. It is a supplement for reptiles who are not eating well and an appetite stimulant. Feed your crickets Orange slices so that he gets plenty of Vitamin C through eating them. Also you might want to alter your heating level to a bit lower and increase your humidity. I am in no way a vet but I do have lots of experience with all types of reptiles due to our petstore in ATL. Ga.
http://www.tropicalfishatlanta.com Tropical Fish Atlanta Pet Center. I work only with the reptiles and mammals.
Hope my suggestions help!?!