-Put on a nice outfit -Smile when you greet H -Be sure to break the heavy discussion with light, fun comments and jokes as appropriate -Be sure to focus on working together as a team--"how can we face this together? what are your thoughts/ideas?" -H can come up with some solutions -Be sure to have the spotlight on YOU two not on the OW -Calm, cool, and collected
At the end of the convo, I would give H the After The Affair book by Janis Abrahms Spring and ask that he read it as a part of "doing whatever it takes" to work on the M. I'd suggest that you buy the book at the local Barnes and Noble store if you can.
Use this ^^ approach only if H has shown openness about the OW and the office move. If not, then I would hold off on giving him the book.