There is no way to predict legal costs.
The whole thing cost me a lot of money and we didn't even go to court. It cost me $50k to agree with him - he kept changing the terms of settlement and I kept responding, agreeing again only to have him change it again. Several times.
He was milking me dry on purpose. I ended up getting what I would have on a bad day in court but it cost be 4x what it needed to.
What does your L say? Do you have a mortgage? Is he paying anything towards that? If it goes into receivership it impacts him too. He is obligated to pay it too if he's on the mortgage. I wouldn't agree to selling/renting unless/until you come to an agreement about he rest. Would it be an option that might force his hand here?
Don't worry about his contact details - I would be worried if he thinks he's entitled to,rack up legal costs for you by constantly contacting your L. He needs to have his L contact yours.
If you have children you need to contact the Child Support Agency and start that process. That isn't so,etching he agrees to - it is set. There's a calculator online.
Are you eligible for Legal Aid? Do they cover Family Law issues?