I think I would preface your comments with something like:
"I want to bring up something that is very important to me, and I want to be heard. What I am going to say is not an attack, so I don't want a defense or excuses. I just want to say what I feel needs to happen to move forward in this M, and I'm not prepared to move forward unless it does. It is non-negotiable for me. Again, I don't really care about defenses & excuses. That isn't important for me & I really don't care, so please just listen."
Now hit him with the knowing that there is still contact. Real healing cannot continue while this contact goes on. I am not prepared to attempt it until that is a reality.
Now, if it is not non-negotiable condition for going forward, don't make that an ultimatum that you won't enforce (but it sounds like you are at that point), but you've read the healing from infidelity chapter (hopefully recently again), so you know what it takes.
Just my 2 cents.
Good luck. Maybe have something after the MC to do to soothe and care of your self & the tension. Something wo/ the H. Friends, book a massage, etc.
Me: 50 W:43 S6, S3 M: 12 yrs. T: 17 M is bad & Not happy Bomb Mar '14 S 5 Feb '15 D Bomb 13 Apr '15 (but "no hurry") DB Coach May '15 Wants proceed on D Aug '15 Starting 1-on-1 negotiations Sept '15