Personally, I say it would be crazy to use a mediator in Divorce, unless you have nothing to loose, no home no kid no pension, no savings.
Otherwise you will get screwed, it will drag out for a longer time, and you will end up having to hire an attorney anyway.
This man has proven one thing. His word is useless, so him saying he wants to work it out without lawyers really means, give me everything I want, and let me do whatever I want when I want, and if you don't then we are going to have a problem, and you are the unreasonable one.
I say it's well worth the money now. He will know you aren't to be messed with, that you are strong, and that you are not going to take this lying down.