Upside Down, I am sorry you are here, but glad that you came looking for help. This is a good place with lots of people that have had similar issues. From your post, it is very clear that you have lots of expectations from your husband - statements like you are not the problem and can't fix the problem etc. First is a realization and acceptance that you contributed in some measure to what happened and work on fixing that. Making yourself happy is an important aspect as well and I am glad you are working on it. You might want to buy a copy of Divorce Remedy (paper back around $14) and read it at least a couple of times. As for your H, he is burying himself at work (trust me, I am not supportive of his actions) partly because of the demands of work and partly because he is finding more joy there. Next time, he levels accusations at you, listen and don't get defensive. While 90% of what he says might be said in anger, you might get some clues from the remaining 10%. I was very guilty of doing similar things and my wife responded with a tremendous amount of anger and closed the door on me - we are in a much happier place, but it did take a significant amount of resolve (it hurts to be repeatedly called the bad guy when you are trying to work on some thing that you know is going to help both of you as you well know). This is going to be a long journey, but the first step is to lovingly detach - exactly how to go about it, you will discover on your own. Another book you might want to get is "The 5 love languages". Unfortunately, you are going to have to do a lot of hard work - I see a lot of pluses for you though, there is no EA/PA and your H is willing to go through MC. Make sure that you work on yourself in the meanwhile - he will see the changes, might get upset initially that it took this kind of a threat, but then they do eventually come around - look at the piecing BB for some good success stories.
