Can a narcissist father receive 50/50 custody?

I am currently fighting to keep joint custody of my children. The father left me when I was about a month pregnant and has been fighting and manipulating me ever since. One child is 8 years old and the other is 3 months. He wants shared custody. We already have joint custody set for both. He is trying to take away my domiciliary rights but there is no basis on why he wants to take them from me and will not give up. He has the MONEY, I don't. That's what it's all about. He has always been an alcoholic and substance abuser since I've known him, about 10 years. He was not around much to take care of my oldest daughter when she was younger. When she got old enough to take care of herself, he became her playmate at best. Therefore, she likes to spend time with him. He does not make her do anything she doesnt want to do. There were a few incidents where he put her in danger such as drinking and driving. Furthermore, he claims to be a better man and attributes his change to his mistress that i found out about after the separation. I caught on to his manipulation by him texting me asking why I want to take the kids away from him so that he can have proof... He accuses me of same things that he actually does. I wish he WAS sincere and a better person for the sake of the kids but he is a true narssisist and a fake. No one else can see this! When will the truth come out? I am constantly defending myself so that I won't lose my kids and I have never done anything wrong! As far as the infant, he has tried to take her from my house since she was 7 days old and I was breastfeeding. What else can I do?