Well not an easy sitch to be in right now...but you must be doing something right to be there...I will eagerly be reading your posts to see how this sitch pans out and offer advice when I can.
I try to think of what advice I would need...maybe try not to be the first one to talk, I know I could see myself trying to control the session, and would not want H to be pushed to soon for his comfort, let the MC be the guide. I think you might be looking at having to do all the work with guiding the communication like you have since BD and I am sure before, such as I have.
But trust that the MC will help the conversation a long, if he feels H is not opening up or saying it is 'too late' a good MC will confront him on whether or not it is. Pointing out the behaviors that conflict with H's statements. My IC did this to me yesterday
Sounds like this MC puts people in spots that they need to look deeper...he did it to you already and called you out on it, setting boundaries early and says he has a lot of experience with MC.
I can imagine not mindreading in this sitch leading up to it...so hard, but try to catch yourself in that mindset and move on. I do know why it is so hard though, because they do not talk...my H did not tell me his plans with money and support, making me question last night if he was taking his whole pay check and running, well he did not and gave me plenty of money for bills and a little extra. Now if we had good communication skills and comfort he could have told me what he was really doing and I would not have been stressing last night. Now to back track and thank H for taking care of S and I through the process. I have done this but need to do it again.