My daughter is living with me. My X say's it's not leagally?

Since my 13 year old daughter is now living with me full time and I am trying to get child support, my x say's that she is not living here legally. We always had joint legal with him being the primary caregiver. I have always taken care of her money wise as much as he asked for, given I am on disability and he is a full time RN. He agreed in the beginning that when she got to be a teenager and wanted to live with me it would be o.k. But now that she is here he said absolutely NO financial help will be coming from him. He said if I try to get anything he will make her move back home to him. I am home all day and he is gone 10 hours a day. She WANTS to be here and the thought of going back to him makes her have little panic attacks and she cry"s alot. Most of the time when he is home he is past out from drugs. It is not safe there. Her grandma just moved out (she had lived there and took care of my daughter) she knew it was the time to go and wanted to see her with me. So I need to know if he can just take her from me, she changed school district's and is starting a new life here. R can he choose to not help me? He is making it difficult because I make 700 a month and he makes over 3000 a month, I am getting help from my parent's but I think he needs to step up and do his share like I did mine. PLEASE HELP ME FIGURE THIS OUT!