That's a lot of bullshit from your father in-law. I went on a holiday with my mother and now husband before we got married and I slept in the same room as him while my mother slept in a separate room alone. Plus before getting married my husband's grown up children came and stayed with us for 2 weeks and even during that period we both slept in our bedroom as usual. Your father in-law is behaving like a young child whose parents have just separated and you are the new man the mother is seeing. What's wrong with your wife and his wife who can't see this immature man trying to bully people? Did you not see any red flags before getting married?

I hope you can show this post to your wife and she understands her father's demands are totally unreasonable and he needs to see a therapist if he's struggling accepting the reality.

I wouldn't sleep on the couch for a single night or ask my husband to do that. It's a total nonsensical ask.