It sounds to me, based on the words you have chosen, that you feel like you owe your husband something, because he rescued you financially. So now, you feel like you have to rescue him (or his daughter) emotionally. And maybe he also feels like you owe him too. Maybe that's a small part of the reason why he rescued you financially.
Whatever decision you make, stay or go, you will have to accept what follows. And both roads pose its challenges.
If you choose to stay:
There is a website about a highly conscious mom that managed a adoptive son with an emotional disorder. I've read her blogs and found her experience most useful. You can start here: janetajackson.com - Home
I am not sure if your daughter is a RAD child, but what you are going through sounds very much like what Ms Jackson went through. She pulled out of it through the practice of mindfulness (meditation). Her blog entries are old (2 yrs) but their words still have resonance.
I hope it helps you.