I think that's the difference here, PZ - this seems to be a relationship issue, and not an addiction one, which requires a very different approach. With an addict you almost become a carer. With infidelity you're not caretaking the other person and what they do with their freedom is really what will determine the outcome.
Kuraiza raises a really good point. Depending on what his FB use was before, he's cutting loose a lot of other ties, not just his tie to her. It raises more questions than it puts to rest and may be worthy of a further conversation.