I'm going to take a wild shot in the dark and say that he might be slightly narcissistic. He wants you to pull the trigger on divorce so he can tell people he was the victim.

If it were me I would make him do it. The relationship is on life support as is but he wants you to pull the plug because that will enable him to frame the failure in a way that people will still see him in a positive manner. 

It's all about how things *look* with narcissistic people.