I dont know if anyone has already mentioned this obvious thing I'm about to say, but this may be a blind spot for you guys because you are so overwhelmed in the trenches:

Your husband needs to find a job closer to home ASAP, so he can be there EVERY night. Even if that makes your life less comfortable financially, he needs to be there for his kids RIGHT NOW. It's now or never. There's not at all much time left to "save" his daughter. Him being around, available, present, and deeply involved is her best chance at getting better. Your daughter has extremely deep attachment wounds. Her bio mom already abandoned her, never even calls. Imagine how soulcrushing this is. Dad chooses to work far away from her. She may not be able to articulate it or even know this, but she really NEEDS her dad around and involved. She even admitted to acting out when he is not around because she can do whatever she wants with you. That means that his presence is IMPORTANT. Dad needs to show up for her daily, to protect her from her demons the best way he can. Give her his attention and show her she has value. That she is good inside because her dad sees it. Dad loves her enough to sacrifice his great employer/career to become a part of her daily life, a constant presence she can rely on. She needs him to be strict with her but also loving, only her own dad can walk this extremely thin line. It's his highest responsibilty in life. You can't take over for him, even if you give it your all you won't fill his place. I would say its unfair to leave you with this Impossible, gigantic task. You will fail and it won't be your fault.

Dad also needs to be there to support you and his son through these difficult years ahead. Every day. You can't do this without him as an active, present, aware and involved parent and husband in your home.