My ex and I have been legally seperated since December of 2011. Our divorce was final in May 2013. I agreed to her having physical custody of the children ages 12 and 9, but circumstances have since changed. She is addicted to pain killers and has become very sick, weak, and hateful. She verbally gets out of control with the kids. Most of the time my kids are living with her parents because she cannot take care of them. The oldest begs to come live with me and she will not allow it. She does nothing to foster a relationship between the kids and I, and even talks poorly about me to them. My kids are smart and don't fall for her lies, but it makes the situation hard. In my oppinion this is abuse. What are my chances of winning a modifiation of custody case?