Yeah, the 1/4th inch is the absolute largest you can go, but if you have it for the lid of the tub they cannot get the food through the space. So if you have them in a rack system you can't put the food on top, you have to put it in side. I also made storage tubs to keep them in, and I made hoppers for those. They still waste the food and the babies crawl all over it since I used 1/2 inch hardwired cloth (and a 1/4th inch as a lid for it so the little b words won't get out).
Cheap dog food is fine, but I would also use rat food. I feed 1/2 and 1/2 Mazuri and cheap farm dog food. The expensive dog food has a lot more meat than cheap dog food. Cheap is just fine, it's corn and grains, it has more calories and fat because of that.