High earner, what is fair?

Hello, maybe someone can offer some advice. Me and my stbx husband separated recently, he is 45 and I am 43. He is a very high earner £10,000 per month net and annual bonus of £100,000 net. I was a high earner too, we both worked in the city. But after our oldest was born 11 years ago, I gave up my career. She has mild cerebral palsy and it has been a struggle. We have another child as well who is 5 years old now. We have about £300,000 in the family home but not much else. Disabled kids are so expensive. I honestly do not know how I could go back to work. My old career is over, Im so out of date now. Childcare for our daughter would be more than I can earn in a min wage job. Although she is at school for part of the day. Im so tired and hurt and we have no family here and its exhausting. I do not know what to do. What would you say is reasonable to ask for? What should I do? Thank you.