What a shit show OP.
Being firmly emotionally detached from this, I would encourage your husband to move to this new house, financially separate and divorce.
This situation is going to continue on, can't be influenced or fixed by you.
You will never have peace and you are wasting years of your life on the sidelines of your husband's life.
Time to be brave and accept it.
Re your daughter, I think it is time to have a private, quiet chat with your ex husband and find out exactly what he is prepared to offer his daughter.
Armed with this information, sit down with your daughter.
Assure her that you will NOT be hurt by what she wants, that you want her to feel happy, secure, and as settled as possible.
Listen to what she wants and accommodate it as much as possible.
Also assure that it is ok to change her mind in the future.
She is at a difficult age and acknowledging her feels is really important.
She will do better at school if she is happy.
Tell her that she obviously ALWAYS will have a room with you, but it is perfectly normal to sometimes mix things up and try something new to see how it fits.
Of course you will be hurt if she moves out, but if you focus on her needs and how long-term it will hugely help her to get these years with less stress and anxiety, I think you will get through it.