Custody and Visitation Issues: Father Seeking Full Custody. What to Expect and How to Increase My Chances

I now have a 3 year old daughter. She lives 2 weeks with me and 2 weeks with mom. I am married with a 1 year old daughter as well. I am seeking full custody. My child's mother leaves her with her babysitter for days at a time, sometimes for a whole week. The babysitter, who is a friend of mine, is afraid to testify in court because she fears that the mother will find ANYONE else, qualified or not, to watch our child. The mother has had some shortcomings previously. Some run-ins with the law, some drug issues, and a lot of instability. Recently, she has gotten a job and gotten housing through the state. I have had my job for two and a half years, have reliable vehicles, and rent a house where each child has their own bedroom. My house is loving, safe, and structured. My children know what to expect and we keep on the same schedule most of the time. My 3 year old calls my wife "Mommy". She has been in the picture since my 3 year old was 10 months old. We are very stable and it is almost time for Preschool. I feel like our house would be more beneficial to her development. However, I am told that there is no way that the state of Tennessee will give custody to a father. The mother is not doing anything insanely wrong now other than leaving our child with the babysitter for days/ week at a time. Does anyone have any advice for me? I cannot really afford a lawyer so that makes it all the more difficult. Thank you for your time!

Custody and Visitation Issues: Father Seeking Full Custody. What to Expect and How to Increase My Chances