I think I remember Z_Bube saying he remarried her as well. I don't recall if it was guilt he said made them come together again but I find that hard to believe. If the M was completely severed and they remarried, there must have been some feelings of love/hope/etc to make that happen.
You know I can somewhat relate to your situation Z_Bube. I am saddened that you are still so unhappy with the M, the second time around.
I just posted on my own thread that I cannot imagine going back to a crappy M now that H and I are reconciling. I would leave before living like that again. I know there is no easy answer but I agree that holding on to any guilt is not productive.
No regrets. That is what life is, a learning experience. Your W has made mistakes just as much as you have, A or no A. She has her own destructuve issues that have little to do with you. Own yours and let her own hers.