That is great that your next session is so soon. It is probably the best place to get clear about the details. Any MC worth her/his salt will try to make sure that you aren't walked all over as the vulnerable party. Also, if you bring up wanting to make sure you understand the legal implications before you settle on anything, the MC won't let H get away with trying to make you feel guilty about protecting yourself.
What is your MC strategy? There seems to be little point in arguing about whether to S. (BTW, if you embrace the S as something that could be good for YOU too--which is true--you might just find that H gets the space to question the wisdom of his decision. Unlikely, to change things, but he will at least start to see that he has some doubts himself...)
Perhaps just go in there with the agenda of working out arrangements that are reasonably fair to both of you? Also, I'd really urge you to set some boundaries about how and when you talk about the details. It might be best to work out all the logistics with the MC present.
One final thought -- it will be tempting to hang on to the connectors, those things that force contact. Like, for instance, yardwork or getting mail or sharing a car, etc... Insisting on maintaining these connectors will not be good for anyone. You will each know how to contact the other if you want to. Cut the apron strings FOR YOUR OWN mental health.
