I’m sorry you’re going through this @Shedding123
The argument sounds like the straw that broke the camels back.
You were 26 when you met him, he was 53. He must have thought all his Christmases had come at once. A year later you’re pregnant, so sounds like you wanted a family pretty quickly.
As your son has ASD, it’s probable that your husband does too, that would explain the addictions and long employment during his 20/30s, life was very different then with autism.
With your daughter’s disability, you possibly spent hours looking into treatments, hence the £25,000 medical loan. I suspect your husband didn’t agree to the loan because the treatment wasn’t a recommended NHS one?
You won’t get carers allowance since you earn too much (although I suspect you already know that). If you were to leave you job after the divorce then you would be entitled to Universal Credit, since you have no savings. If you stay in the house, then you won’t get Housing Benefit but if your family home was sold then you could apply (however, you’d then having savings because you’re mortgage free so wouldn’t get UC).
You need specialist legal advice.
You don’t mention Social Services? You need to contact the Children with Disabilities Team. You are entitled to the Carers Assessment as well as your children. If you had some support, such as Direct Payments then you could get help with your caring responsibilities. I can’t see your husband being much help after the divorce.
He sounds like he’s already checked out. He clearly wants a quiet life as this isn’t what he signed up for. He thought he was getting a picture perfect family.
You sound like a great Mum and obviously just want what is best for your children. I wish you luck.