for me, the stage you are in now was the hardest. I never issued and ultimatum, but as FW started moving back toward me and making progress toward being home it was HARD to be patient. I wanted it to happen NOW!
Nearly 7 months of NC with OW now and things are finally starting to settle down. FW is still in MLC (or whatever you want to call it) and has bouts of depression about once a month. He recognizes it and knows what it is, but it still takes a toll on him. He told me in one of his bouts just a few weeks ago that he still thinks about running away. Not running TO anyone, just away. He thinks about his "carefree" lifestyle and says that while he was miserable for a lot of it some of it was really fun (ie- no responsibility and being able to go and do whatever you wanted to whenever you wanted to without worrying about who was watching the kids, money, etc etc). In the same conversation he also said he looks at what we do as a family and as a couple and has a lot of fun doing that too. It's just different. At least now he recognizes the urge to run and realizes that it won't solve anything or make him happier.
It takes time for them to be completely out of everything. FW is now working with his DR. on some depression remedies that don't involve AD's since he had such bad side effects from them (seizures most notably). He's been referred to an endocrinologist and hopes to get some relief soon.
Good luck. Like I said, this is the hardest part (at least it was for me). When you're piecing, but not really and OW is still in the picture. Just be patient and stick to your guns.
BFM
There is only one person who could ever make you happy, and that person is you. David Burns, Intimate Connections