BS here (hope that's OK?)..
Although I haven't been in this exact situation, and am unlikely to be there, as our R is going very well with WS, and has been ever since she changed, started to 'grow up' emotionally, became remorseful, and showed TRUE love to me for the first time in our 10-year relationship (8-year marriage).
But just because I haven't been in that exact same position, doesn't mean the intent/motivation behind your BH's actions involving seeking a D aren't similar to what many of us have felt or do currently feel.
If I had to wager a guess, it sounds like your BH is looking for closure to all this 'madness', and perhaps he doesn't feel he can get true closure from you. That isn't to suggest you haven't been forthright and open, maybe you have. But, maybe what he 'needs' from you is something you either cannot deliver on, or that hasn't been delivered yet. And for a BS, that can leave them in chaos (mentally) and limbo, and it simply isn't sustainable in the long term. So, although he may not truly want to get a D, he may feel that is the only option to end his pain and suffering. Think of it this way: although the D sucks, it would suck WAY more to live the next 1,2,5,10,etc., years in mental chaos and purgatory, in a sense. It may not be that way for you, as a WS (just conjecturing here, I may be totally 'off'), but for your BH, if he is like most all BS' around these forums, then the mental stuff is often described as worse than death (not trying to be overly dramatic, and although I haven't used that term personally, I read it from a LOT of BS').
If you haven't done so already, and if you are truly serious about R, I would STRONGLY suggest you and your BH get into MC IMMEDIATELY! That may be your only chance at salvaging anything.
Lastly, I would strongly recommend talking to him about the mixed messages he is giving you. That doesn't seem consistent with true R. So if he wants R, then he can continue doing what he's doing. But if he wants D, then he needs to stop 'leading you on', in a sense.
Again, just my $0.02.
Best of luck to both of you!