What to do to win full custody of a child when the mother is unfit? 3 Answers as of February 20, 2012

So my husband and I will be heading to court next month for full custody of his 3yr old son. Right now they have 50 50 but its a weird schedule and too much for the child to handle. Also, the mother is unfit. She is using illegal drugs. She has also been arrested for domestic violence twice in front of the child and both cases were dropped. Additionally, the last time we went to court, she failed a drug test for marijuana and the judge threw it out. We have called cps on her and they never went out. We called the cops and they did nothing. We feel the child is in danger. We cannot afford an attorney because we have to pay child support. What can we do to win in court next month?