notsorted, love, have you not seen that he places you in a lose/lose situation at every given point?
If you adopt a softly softly approach, you will (a) get nothing achieved, and/or (b) he'll throw spanners in the works ANYWAY!
If you have warned him, and tried every negotiation possible, then you have to spare all sympathies, as he will toward you. This is NOT your DH. This is Mr Hyde, remember, he adopted Dr Jekyll to trap you.
Who cares if he hates you. he hates you being HAPPY, so why would you listen to his version of who's naughty and who's nice?
TBH, mediation is a waste of your time, their time and resources, he'll never be negotiated with, not ever, so as I have said, stop it. Cite abuse and show them what is said by counsellors of abuse victims to back up your decision to end mediation. Forced mediation is not going to be productive is it?
He doesn't know the right thing to do, the right thing robs him of his entitlement to make you utterly miserable, to hurt and destroy you.
Ultimately notsorted, it really doesn't matter a joy what anyone thinks of you. truly it doesn't. Do what you need to do, sod anyone that gets in your way!