Hello Jules, remembering what happened years ago, especially by your parents having mental breakdowns, is a great concern that has been institutionalised in your past memory and would definitely be a worry you hope doesn't happen again, because people placed in this situation can not be of any support, something you are really worried about.
Your parents must still love each other as your mum isn't moving out, although some uncomfortable truths were said, hopefully, they will work through this and reestablish their marriage, and to expect what did happen years ago will be all different now as time has passed, so try and attach yourself with either or both parent, that will dismiss any anxiety you may be suffering from.
If you are 25 years or under, you can contact Kids Helpline 1800 55 1800 by phone, webchat or online, these people are trained counsellors and they dress in casual clothes, which seems to break down any relationship and talk just as if you are a mate.
You can also ask your parents if they would benefit from some counselling as well, and perhaps you could go with them.
Hope to hear back from you.