@Mrmatrix,
Taking the trust aside.
Respect. I would never have my ex-husband stay at my house, if my now husband was working and could not be there of a night time.. I would find that disrespectul of any man being alone with me at night, whilst my husband was not at home, unless it was a family member.
I also understand your wifes stance. The last thing she wants to hear is, " I want to take leave, I don't trust him".. Because you are in-advertently stating that you don't trust her either, regardless that she is a heavy sleeper.
It is also not un-common, for a "husband" to "try" to have sexual relations with his wife when he feels like doing so, it's his wife. I imagine the first time as she slept through it ( you should laugh because that means he did not wake her up if you get what I mean), that he may have taken advantage of that fact. But, the fact of the matter is, I am sure he can get sex if he wants to elsewhere. I am sure he respects that she has re-married. And, most guys are decent enough not to even consider something so "sinister" because that is what it is right?
I would be approaching your wife on a different note.
I would be backing her up and telling her that you were thinking of her, protecting her, but realised that surely her ex could not be that "sinister" evil.
Then I would say to her, it's also about respect. Just think. If I had been married before and you were working night shifts and my ex-wife stayed here for 4 days and lets even say she still loved me.. Would you find it wrong for me to let her stay here? Or, find alternative accomodation and off course, let her see the children as much as she wanted over that period of time . Another woman in "our" house every night and you weren't here?
In my opinion, the set up arranged was the wrong one but I also think that you have over reacted and have made your wife feel horrible .