I have a gentle suggestion about where to go from here.
Stop talking to them. Stop looking on Facebook. Stop trying to collect evidence against your ex.
I know you think you need to do all this, but really, you don't. The court is going to do what they believe is in the best interests of the child, and may or may not consider your evidence. I know its easy to say this is protecting the child, but is it really? To me, it seems like torture for you.
You've got a great future ahead of you - graduate school - very cool! Do make new friends and keep busy focusing on yourself and your child. Let go of the outcome of this, and the attempts to try to control the situation and make sense of it all. It doesn't make sense; alcoholic-fueled behavior rarely does.
I hope you can take all this as kindness and not harshness. I know it hurts, especially when there's a child involved. But it seems to me doing what you are doing is keeping the wound open and bleeding. Maybe time to let it start to heal?