Property and Equity after divorce, when children are involved

[st68]

I am looking for some advice regarding a financial settlement after divorce. my partner was divorced a few years ago but no financial settlement was agreed on even though they attended mediation.
My partner has 4 children with his ex wife the youngest being 11 and the eldest 16. There is quite abit of equity in the property and my partner said that his ex could have 75% but 25% had to go into trust for his youngest daughter who is disabled and will need lifetime care.
His ex wife disagreed and wanted it all so no agreement was reached.
she still lives in the property with the children and my partner pays above the going rate in maintenance but she keeps defaulting on mortgage payments and the account is in arrears and they now owe more than the original mortgage. She has also run up debts in my partners name and he has acquired ccjs that he was unaware of because all correspondence goes to his ex wife. it has been proven that she is accumulating debt in his name but he refuses to have her arrested because of the children.
He cannot get credit of any kind because of the ccjs and mortgage and cannot even rent privately because of the credit checks, which makes it impossible for him to have somewhere permanent to take his children when he has them regularly.
she cannot afford to buy him out but if the property was sold she would have enough to rent privately because of the amount of equity in the property but she refuses to sell because she says she doesnt want to have to live off her own money, she will lose all benefits etc.
Any advice would be greatly appreciated so that we can just move forward and cut all financial ties with this woman, Thank you in advance xxx

If she and he can't agree at mediation then it has to be to court for a decision but it's expensive so avoid if at all possible.

I think he should just have agreed equity at 100% as he his wife is likely to put their daughters interests first.
Could he now agree equity? What % does he pay of his salary per month?

Does he have a pension? If so this needs to be offset with the equity and since they have 4 DC she is likely to get more than 50%.

He needs to apply to court and sell the house. Clearly it isn't affordable for her.

He's been mugged off and should have taken it to court a long time ago. Not sure if this is financial abuse as they're divorced, but I think a court would look poorly on XW having screwed her XH over through lack of financial control.

He pays more than csa says he should, which she agreed to because she didn't want the dwp involved. she doesn't really have the daughters interests at heart, she is constantly in respite when she is not with us, she is just bitter at my ex and her children are her gravy train now that my partner has left. He doesn't have a pension in place and will not even take out life insurance until the financial settlement is in place. She goes on holidays etc but doesn't pay the mortgage and runs up bills, just to aggravate my partner I think, it just seems so unfair on some men x