Shay - I am reminded of something I read last night in a book about obsessive compulsive disorder (which is not the same as anorexia but there are a lot of similarities and overlap).
The book made the distinction betwee a lapse, a relapse, and a collapse. To me, your H's behavior here falls somewhere between a lapse and a relapse - so don't make it into a collapse. Setbacks are normal. Recognize that (and helping him recognize that) and be aware that you don't have to go all the way back to square one.
