Modify Custody?

I had language included in my custody agreement that precludes either party from using alcohol or other substances to the point where they cannot care for the child. After the order was entered, I let my ex move back in because she was at a point where she said she had a problem, wanted to quit, and wanted to get help. She got treatment at Holly Hill. Since that time, she has had several relapses. She is now at a point where she says she doesn’t have a problem, doesn’t want help, and wants to drink alcohol as she pleases. There have been five instances where she has gotten drunk and out of control to the point where she cannot care for the child. There have been more, but there are five recent ones that have been witnessed by other parties. What kind of motion can I file to either modify custody or force her into treatment? Is there a way to get her back out of my house?

At what point can I show grounds for divorce from bed and board because of alcohol use? What is an excessive user of alcohol, and when does my life become intolerable and burdensome because of her drinking?

You should file an action for divorce from bed and board to have her ordered out of the house based in her habitual drunkenness.
You then need to file a motion to modify custody based on the substantial changes that have occurred since the last order was entered.