Catso, please don't thake this the wrong way but since your situation is complicated by the financial obligations and children surely you have a lawyer who deals with your divoirce and who should have explained all this to you. If not get one ASAP.
Your entire situation needs to be taken into consideration, which is why you would not be able to get a complete advice in here. Still, as far as I am aware you are under no obligation to pay for the mortgage and! the maintenance and you can't make her sell. Get a lawyer and all the best of luck. I am sorry you have to go through this but don't forget she would have a lot more responsibilities then you so don't blame her for trying. Despite the kids being involved it is a business transaction treat it as such and keep your emotions out of it.
Good Luck. S.