Info On Getting Full Custody

My question involves a child custody case from the State of:kentucky or ohio

I have a 3 year old son that lives with his mother in kentucky, over the past 3 years she has done nothing but stay in trouble for drugs, traffic offenses, domestic violence,etc. I pay support and provide insurance for my son and she does nothing. She doesnt have a job and has only had one job the whole time he has been alive. That lasted a whole 2 weeks! Her excuse is seh doesnt have a sitter but she manages to find a sitter everynight so she can go to the club and get drunk. She has been off and on TANF since my son was born and when she is on the system they take the child support payments that i make and give her a check. She knows this and every month she calls me and threatens to take me to court for not paying support and unpaid medical bills that she is supposed to be paying 50%of. She is living in ky and drawing out of ohio. She uses her moms address and doesnt live there because the apartment manager doesnt allow her on the property due to the drug traffic and the domestic violence. She is living with her dad in ky because she has nowhere else to go and they have called CPS on her claiming she is neglecting her kids. I would like to get full custody of my son. He has seen and heard too much while being with her. He is 3 years old and pretends like he is smoking crack. I have heard that the courts never side with the father and that sometimes they will give the kid to the grandparent first. also i dont know where to file since she is living in one state and the support order is in another. i just need some advice. :wallbang::confused: