Really sorry you are in this situation OP, and he sounds a total bastard.
Have you had meetings with a couple of brokers and explored options such as borrowing the extra you need but lengthening the term?
Are you taking advantage of your single occupancy council tax discount?
I have had to leave a home I loved, and I get that it is your security, your home during what has been a horrible time.
But once I realised I had no choice, I had to get on with it, and though the process itself was horrible and stressful, my new home quickly became my home, my security, my sanctuary, and a place ex had never set foot in. The kids were able to influence their new bedrooms etc.
Plus, bills are so much cheaper. Lower CT band, lower insurance, energy etc.
Your income is not high: prioritise quality of life and independence with your own finances?
And thank god you are not married: he could have ended up with 40 or 50% of the value of the house!