Gestation period is 21 days. So about every 20-23 days you'll have a new litter from that individual mother. Babies will grow from pinkies to weanlings in 21 days as well, but I would keep them with their mom a little longer.
Don't take the male out. There is no need for it. In this style of breeding, the females will be pregnant all the time.
I feed my mice pork grower. you can go to your local feed store and see what they have and try stuff out. Or go the more expensive route and buy mazuri or the like. I also give them a little bit of dog food every now and then, no dyes.
I have colonies of 1:3. I haven't had 1:5 but from just watching my groups right now, I think 5 females would start to push the boundary.
I keep my mice on kiln-dried pine shavings. The kiln-dried part is rather important as I believe if it isn't dried, the fumes from the wood will cause respiratory problems in your stock.
If your mommas eat their first or even second litter, don't give up on them! They just don't have the hang of it yet. After the third eaten litter, I would feed them off and start over.
I don't know when I replace breeders. Just when I notice them looking tired or just old. So probably before I even need to.
Build a rack if you are going to get more eventually, or if you don't mind spending the money. Soooo much more easier than tanks..
I hope this helps!!