He sounds terrible. You and him are just seeing each other a few months. He knows that you are having a hard time with your daughter and trying to figure out what to do.
He wants her gone their so you can have more time for him. He also does not want to hear about your problems or offer any support to you.
At this stage I tell him it over as it not working out between you. Tell him you can see he wants to be with a woman with no kids but unfortunately for him you're putting you and your daughter 1st.
I think that you need to get your daughter assessed for ADHD and autism as well. Autism presents different in girls. They can mask (cover it up) well in primary school but as they get older it harder. It becomes more apparent and they can appear different to other girls of the same age. I look at the autism society UK website to get more information.
Your daughter sounds similar to a girl child (X) I know. X found it hard to make friends. Their were other signs that something was wrong with X that became more pronounced as she got older. She was diagnosed as being on the autism spectrum.
When X went to secondary school her parents had a good chat with the school principal re her diagnosis, what she was like and she got the help she required.
A few years ago X would not want to get involved in sport, go places or do thing's and socially she was poor. She would get anxiety about things that another child would take in their stride.
Getting her involved in sport let her make friends. Get the autism diagnosis enabled her to get the help she needed.
Now X will be doing her A levels next year. She is planning to leave home to go to university.
She is doing well in school. She has friends their and through sport. She has a boyfriend.
I knew she had a hard time and her parents were worried about her but with the right help she is now in a good place.
I would go private to get your daughter assessed for ASD and ADHD. Regarding school I would ask her what she like to do after leaving school. Perhaps she is better at more practical subjects than learning ones. Getting her though school and letting her do GCSE is important because this stage will lead her to courses, college or university than will lead her to a job.
I would chat to the school principal and see what think regarding what exams your daughter could and should do. Perhaps she could drop 1 or 2 subjects and that might help her re school and her anxiety. I also block certain sites on her mobile so she can just make and receive calls. FB, snap chat ect could be making her feel worse or making her anxiety worse.
I think that you also need to push your daughter a bit into going places or doing things.
It won't be easy but unless you do this I think she could end up finding adulthood hard re going to college, making friends and getting and keeping a job harder.
I would speak to you doctor as well about her and what she is like at the moment. Maybe your doctor could give her a physical check up and blood tests and suggest some medication that could help her.