I left and continued to pay the mortgage while also paying rent on my own place (no DC which made it a lot easier). I lost out to the tune of £000s when the house was sold, etc., but I actually consider it a price well worth paying for the sake of my sanity. Had I stayed it would have been unbearable.
However, I was younger, child-free, in a good job and secure in the knowledge that the rest of my life was ahead of me and nothing could stand in my way of making a success of it.
Having also left a later relationship with DC in tow and leaving the family home with no claim on it, it was significantly harder and swallowing the financial loss was not as easy. However, again I felt the psychological cost of 'fighting' was not worth the spoils, and although I again lost out, I've put it behind me and moved on.
It comes down to how much you really need what you might lose and the emotional/practical sacrifices made by fighting compared to the financial sacrifice made by walking away. Also bear in mind that there will be a financial loss inherent in fighting now that legal aid for family law is so restricted.
Sorry you're going through this and hope it works out.