Biters do breed biters! It is simple genetics. If handled the same, mice that bite more readily and/or frequently will pass the gene that causes them to have a propensity to bite. Defensiveness and aggressive behavior can absolutely be passed along. I have bred anywhere from 200 to 5,000 rats & mice every month since 1980 and this has been my observation. I never breed biters. They die immediately and I now get bit like once a year. Animals of the exact subspecies have been bred for things like aggressiveness for centuries by simply breeing aggressive animals with each other or vice versa for calm animals.
Mice for balls works fine for me! I ONLY feed mice to my balls and all my rosies and colubrids. I have balls that are 3 years old and 1800-2600 grams and gravid this year. On mice ONLY, my balls have near perfect growth rate, no obesity, perfect stools, faster digestion, no problems with meal size and breed well (we'll see how the eggs look any day now but I bet they will be just fine). With mice I get less mess, less odor, less expense, easier freeze and thaw, they take up less room, etc. I rarely have to buy mice and when I do it is only in the summer and fall when they eat like piggies.
This is my opinion based on observation during 30 years of breeding boas, pythons, colubrids and a few other reps. While this is my first year breeding balls (weird I know), I have bred 30 species/subspecies of colubrids, rosies, boas, bloods, savus and some others. To date I have produced over 2,000 snakes and over 150,000 rodents.
Oh yeah, I never leave weanies with a new litter of pinks. Hard on the pinkies.
I hope this info helps and good luck with the breeding.
Kevin