Moss is added to keep humidity up. But there is a high risk of impaction when using moss. I avoid it.

Your frog's diet should be composed primarily of things like crickets, roaches, and earth worms. Rodents can be fed as a treat occasionally (no more than twice a month). As for dusting, it is possible to over-supplement your frog. Dust once to twice a week max. If you gut-load the insects with nutritious foods high in calcium (which is best), just dust once a week.