I was having a similar issue with my crickets too until I increased the airflow! As long as I keep enough food and water in with them, they don't eat one another and the only dead ones I find are the older ones, usually the females after they have laid their eggs! As far as controlling the humidity... I've been thinking about adding a charcoal pouch into their container. Charcoal is great for absorbing moisture and also cleaning the air and helps keep it smelling fresher. I wonder if anyone else has ever tried that???