If there's one way to make sure your child doesn't want to stay with you, it's moving them into your bedroom while you take the sofa. Not even a sofa bed, I think? I can just imagine Jack and her crumbling bones playing the martyr with SB over this. "Oh don't worry about me, I'm sure the sofa will be fine". Now, I get why people do this through necessity, to give kids privacy and space of their own (been there myself) but she doesn't bloody need to do it at all, and her personality doesn't match with playing it down for the kid's sake.
If she's for real (I don't think she is) about going into a 1 bed, she runs the risk of him choosing not to visit her much anymore as he gets older.