Now you have remembered more incidents, Northern, there's no way you can view this as a 'one off' or isolated incident, is there? I think you need to tell someone now, because your daughters are potentially at risk - both of them - and you must do something to safeguard your children.
I think you should seriously consider phoning children's services yourself, and asking for help. If not them, then your GP. There will be a child protection/safeguarding concern raised in any case, as soon as you talk to anyone, or your DD discloses to anyone like a teacher. There may have been one already, depending on what your DD and/or DW have already disclosed.
Children's services will make an assessment of whether the children are safe. If they find two parents who are 'hiding' what is happening, they will conclude neither of you can keep them safe... It would be far better to work with them, and take their advice and support.
There have already been two serious incidents (at least?) - a head injury and a throttling - and so far you have not disclosed or sought help. It sounds like your daughter didn't get medical attention following a head injury. That mustn't happen again.
It would be best for your wife to seek help herself, because children's services will want to be satisfied that she acknowledges the problem, is getting help and has strategies to stop herself hurting anyone. But if she won't do that, right now, you really must seek help yourself. It will be seen - as it is - as a sign that you take this seriously, and can and will keep your children safe.
It's a terrible situation to find yourself in, and telling someone will not be easy. But it's less terrible and difficult to tell someone than to do nothing.
Good luck.