I get that. The good times and then there is a tilt to the bad but it sneaks up on you. Happened to me to with my husband when he was using and drinking. He became abusive to me and still I stayed for too long. And now he is in therapy and not abusive and seems changed, but is it still logical to stay? I understand these are not easy choices, and its sometimes a slow progression.
I can see adoption as being a link for you too, at least somewhat. Im sure she does have good qualities too, and its like a push and pull for all of us.
Good luck to you.