It is hard in you current situation now. I understand how you feel. But you will have to go through with it.
Even after 9 months S, I still felt down when discussing about D. But there is no way back. In the last 9 months, my W only contacted my D through sms. Not even had the time to call. Ocassionally she had lunch/dinner with the kids. My S did not want to reply my W's sms. I found out from my W last week when I asked her why she did not talk to my S. Can she feel happy? Maybe if she doesn't care about our kids. It seems that the om is more important than anything for her. Goodluck for her if it can last forever.
If your H does not want to give up the ow, after 3.5 years, you have to reconsider your options. DO you still have the patience to wait until he wakes up? If yes, continue DBing as best as you could. It not, you have to make a hard decision to let go your M. Only you can make decision on this one.
In Australia, unfortunately there is no fault D here. I think it encourages people to have A as it does bear any financial consequences. Having A is a breach of a M contract. It should be punished with penalty like in a commercial world. Otherwise what is the purpose to get married. If both parties can't continue the M, they could end with mutual agreement. ANd then the parties are free to find another partner. But not before the M is ended.