I don't think you should cull the dominant female until its confirmed she's dangerous to other mice. The old female is probably only attacking the younger female because she's thinking its a strange mouse that could harm her babies. I'm sure she'll be friendly with her once the litter is weaned. I have a female who is ONLY aggressive when she has pups. She's even nippy with girls who she snuggles with when pups aren't present.
You can give your mice a break from breeding. But its not necessary.
And you can keep the male with the colony. My friend has females that have killed another mama's litter. So killings can go either gender...
Good luck
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