@Solstice47,
I'm quietly listening, but I'll pipe in to say that I have experienced something similar in my extended family, the mother sending the child to friends' places while she used the support money for coke and heroin at different times. I found that part out late in the scenario. She got custody in the first place because of a ruse, which, years later she apologized to me for (I talked with her at length several times before she died).
Anyway, from how I am reading what you are saying, I think:
1) see an attorney who is conversant with this kind of situation (that is vital, believe me); my family member dealing with all this used his divorce attorney, in that case a poor choice.
2) and, with the attorney, consider an investigator.