NMC, I don't think you talked very much about your H's background. Did he have a healthy upbringing? Does he have any long-term record of emotional problems (other than his obsession with his ex)? Is he a reasonably healthy, balanced person, with good work habits and a decent network of friends? Any substance abuse or history of violence?
Very, very pertinent questions. Ones that I wish I had found out about my ex.
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.