I know how unfair and hopeless things feel. But he's living in his own personal hell, even though it doesn't look like it from your end. Let him live and suffer there. He's a big boy.
And I know you will tire of hearing it - if you haven't already - but it's the best advice out there: keep focusing on you. Keep focusing on being the best person and mom you can be. Please stay as distracted as possible and do the things that make you feel accomplished, like taking amazing care of your D. Please trust me when I say this will work. It will take time. But it will work. And one day soon, you won't care what your H is doing. Or, you'll start caring less.
One of my favorite quotes, just for you tonight, Ss:
“I beg you to have patience with everything unresolved in your heart and to try to love the questions themselves as if they were locked rooms or books written in a very foreign language. Don’t search for the answers, which could not be given to you now, because you would not be able to live them. And the point is to live everything. Live the questions now. Perhaps then, someday far in the future, you will gradually, without even noticing it, live your way into the answer.” (Rainer Maria Rilke)
Hugs.
M: 40 H: 44 Married 14 years S11 & D6; D20 & D19 from previous M 2BDs/PAs, 8 years apart Piecing: April 2014