1. For about 6 months I used a commercial vegetarian cricket food, but when I ran out I followed a recipe online using cat food as a base. However, I did some research and found some evidence that using animal protein can lead to gout in reptiles, so I've since switched to a mix of ground rabbit pellets, oats, sunflower, flax seed, rice puffs and cheerios and whatever other grains I have lying around.
2.It's worked just fine for me. I've had 3 deaths in the past 8 months or so.
3. I'm only feeding 2 animals, so I try to keep it around 500 in an 18 gallon Rubbermaid.
4. I just put 2 or 3 full egg crates in.
5. I put water gel in the lid of an old butter container and throw dry chow, veggies and fruits directly on the tub floor.