I know it goes against DB principles to try to change someone else.
Actually, DR says the exact opposite. It says that changing people is actually the goal of DR. It's just that you do that by first changing yourself.
I am not going to respond to each of your thoughts because one of them really stood out to me:
Someone posted something to me once, that DB is for couples who have had an overall good R and then ran into trouble.
Really? So how long did the M have to be good versus the time it was bad to qualify? In who's mind does it have to have been good/bad. Do both partners need to feel the same way about the M overall? My point is that in the case of a WAS, they almost universally feel the marriage has ALWAYS been bad. Forgive me, but that is sorta what you were, and you may still have those feelings that led to your "indiscretion". It is usually not so bad as the WAS thinks, nor nearly as good as the LBS thinks.
You know, really, before this post, I kinda forgot for a second that you probably had feelings, well you DID have feelings that led to OM and such. I think those feelings never went away and now, after so long of a battle trying single-handedly to fix your M, you are having some of the same negative feelings about your H and M.
It's just so sad that your H cannot find the strength/resources/whatever to see your effort for what it is. I'm sure that if he could, some of this feeling that the R/M was never really that good, and the negative feelings you are having towards him would fade a bit.
Just an aside from my sitch that I think may help you...
In my C session yesterday, I said to my C that I felt like somehow I was trying to win my W back and how much that sucked because SHE's the one who cheated on ME. I went on to say that I understood that whatever pain she inflicted and wrong she did to me, there was a valid reason in her mind to do it. She got to that point with my help and I needed to remove my part of the barrier to allow her to come back. Of course, it's then up to her to win ME back, but we're not there yet.
My point is, and you know this, your H played a part in all this, from however long ago it started to go sour, to now and until he gets over himself long enough to see that, things will be much more difficult. He is wallowing in his pain and anger, and has been for over a year now. Understandable I guess, but unfortunate as well.
For you, I guess I hope you can continue to find the positive in things like you are now. I really think it will infuse life into you and maybe your H in turn. Who knows. I am proud of you for sticking it out this long and more power to you to continue as long as you are willing to.