Hi, ADs might help, but he is still in MLC. And I also sense that a bit of you feels it was the OW. My take on this, is if not this one, someone else. A lot of LBS in the early stages tend to think, 'If only they hadn't met OP' What I see now much later on, is that someone or something would have found these MCLers.
My xh's OW definitely wanted my life, hated me etc etc. But he is done with her, and STILL in MLC [took 6 years to finally end, and a gazillion break-ups] Even now I wouldn't put it past either of them to hook up again. Crazy seeks out crazy.
People say 5-7 years. I thin if it is a real MLC rather than a 'difficult transition' it takes all of that, and some of them are stuck forever.
But if you h is 'simply' having a hard transition from one part of his life to another, and depressed about it, he may well work through it much sooner. He is still in the same house and still speaks to you. Mine took off, and only contacted me sporadically to spew. I haven't seen him [apart from briefly in Court 15 months ago], for two years now.
There are degrees of MLC I believe, although they share many of the same characteristics in the earlier stages. The hard cases just cannot face their issues. The old ties and loves seem eventually to pull the less severe cases back to their loved ones. It is a good sign that your husband still loves his grandkids, some don't even care about them!!