Was the sex on the couch a boundary break or did it just unnerve him? My fiance heard my deep breaths (supposedly) over a loud movie I was playing while Budkep and I slept together one night when we all came to visit him. It was not a boundary break, but it did freak him out. It came down to dealing with the emotions of it, but also accepting that this is going to happen seeing as he wanted us to all move in together too.
Also, have you thought about if there is any connection to not wanting to live with mono and his break up with Roly?