This is a job for Legal Aid, because (I believe) you cannot do this without a lawyer. I went to google and entered "legal aid divorce" and the name of the major city closest to me, and got the names of the non-profit organizations that set people up with help. That's what you need to do. If that doesn't get you the right names, try calling a DV hotline and tell them the truth--that you're looking for a referral to legal aid.
It's not clear enough that there is really a problem that CPS should be involved in here.
What are the specific reasons that your DD doesn't want to go to their home? If its serious (not an issue of rather being with her friends or something), maybe you could check into emancipation for minors. I'm not sure if you can be emancipated from just one parent, but I'd check into it. Also not sure if there's some minimum age. The cases I've heard of have been older, like 15 I think.
I'm also not clear about what you'd be calling CPS about exactly. Is her dad repeatedly getting drunk to the point that he's scary to be around or cannot make a safe home for her? Does he drive with her when he's been drinking? I think drinking alone is not an offense that CPS is going to care about, but driving with her in the car or being violent when he's drunk, or if she's neglected because of it, there might be something they could do (though I do think their being cops cuts against that). I wouldn't feel happy about having her step-sibs smoking pot around her, but I don't really think that is CPS-worthy. I may be kinda skewed on that one though, as I remember my grandmother teaching me how to pick the seeds out of her pot. She was a pill. An awful lot of my mom's friends were regular pot smokers and I was around it quite a bit when I was young and, truthfully, I don't see it as a big deal. If it were harder drugs, I would be more worried, but alcohol scares me a lot more than pot -- both in terms of the behavior it causes and the danger it poses for kids who get their hands on it.
I don't know if anything would come of it, but if the other kids are smoking pot around her, could you bring her to the doctor when you get her back from a visit? I don't think they'd be able to actually DO anything for her, other than tell her to move away from the smoke and go over the dangers of drugs, but it'd start a paper trail at least. Maybe the doctor would call CPS on them?