I still believe you H doesn't know what he wants and he filed to help you. I know you feel that the D will proceed because the wheels are in motion. You have told your H and your L that this isn't what you want but at the same time you believe that this is what you need to do...so can you just not do anything to help the D along?
My H and I went to the C last night. It was so interesting listening to him talk about what he has been feeling for the last couple of years and so much of it fit into the MLC stages...and I have to say I was impressed at how my H was able to work through so many of his feeling on his own. I really had no idea he had processed as much as he had. There is something going on with your H beneath the surface and you really have no idea what could be. You know I think that your H's filing could be something turn into something positive because he has been stuck and avoidant...and although filing for the D isn't the movement toward, it is movement. You can see that your H is physically affected by the emotional turmoil he is in. If you can, keep validating your H's feelings. Let him know that regardless of what happens, you are sorry that you didn't listen and you weren't there for him the way he needed you to be. I still believe your H cares for you and wants to keep the connection but at the same time he wants to escape the pain he is feeling...and he is trying to keep from hurting you any more than he has.
Who knows what will happen in the future...and IMO, you are doing the right thing by being open to the possibilities. You want your M but you are realistic that the odds maybe against you. You know your H isn't emotionally capable of being in a real relationship now so you are moving forward with your life. Not that I am any expert but I think you are handling things in the healthiest way possible.