Get legal advice. There are a number of resources locally that might be able to help you sort through this, if you look up your local community centre they might be able to offer you some sort of counselling to help you sort through it.

From a legal standpoint, here's a checklist.

https://www.citizensadvice.org.uk/family/how-to-separate1/getting-a-divorce-or-dissolution/#:~:text=You%20can%20call%20Refuge%20or,2000%20247%20at%20any%20time.

When you describe your husband, you mentioned his being on the spectrum - this might influence his behaviour, but being neurodivergent is no excuse to be an arsehole. That is a CHOICE that he is making.

You are absolutely in an emotionally abusive relationship, if your daughter is begging you to get out, it's WAY past time for you to have made a move. Every day you stay with him is giving him another opportunity to hurt and emotionally stunt your daughter.

I absolutely give you props for posting here, this is a hard decision to make, and you've already made the first step. Keep the momentum going, actually make a plan to leave. Figure out what you are entitled to in terms of child support payments and talk to someone in social services about the likelihood of housing support, and what paths to follow.

Good luck.

There is really only one solution to this. You tell your Mum that upon reflection, she can't move in to your place either, based on her complete disregard for your boundaries/house rules the last time she stayed. Help her find a place, sure, but don't take her in. She has a couch for a few days.

Tell Fiance that you weren't thinking straight and that he is right. It has to be you two making decisions as a couple. ASK him if it is ok if she spends a week on the couch while she organises a place. Do not allow her to move in.

It is not your responsibility to cover for your MOTHER'S fk-ups and lack of planning.

Here's a suggestion. Experiment with other milks. Oat milk, nut milk, rice milk. It's not the same, but it's an ok substitute if you find the right flavourings that you like, eg chai tea or some such.
You don't have to drink milk before bed, have a herbal tea or kombucha or

Being lactose intolerant and drinking milk doesn't just give you stomach pain and diarrhea, it can cause lasting damage to your intestinal linings and lead to chronic illness.

Do yourself a favour and stop giving yourself the shits just because you like the taste.

You are in love with your dream of what the relationship could be, not what it was.
You've cut a clean break, let it rest.

DO NOT SEND IT

It's wishy-washy and full of "poor me" and drama. It makes you sound like hard work. Just don't.

The cringiest.

As an ex-RN, and past Mum of troubled teens, you have done nothing wrong.

If anything, you should be proud of yourself for teaching skills that lead to resilience and survival.

If you had not given this teen the confidence to survive in the wild, they may have ended up on the streets, which has a much higher chance of an unhappy ending.
You should be giving yourself a pat on the back, not castigating yourself. You are doing a good thing, continue to do it. You are giving these kids a valuable skillset, and building their self-confidence.

The mother is panicking and looking for a scapegoat, because it can't possibly be her parenting that is to blame here. The fact that her daughter ran away instead of talking to her speaks volumes. You are part of the solution, not the problem.

You are not alone. As a nursing student on a hospital rotation, I did exactly the same thing, for the same reason.

I think my face was as red as the button.