Arsene, I'm sorry you're going through this. I wish I could do something...I do have some ideas/thoughts for you. First, sleep is so important to battle depression. I know it's hard to stop the stream of thoughts that come to your head when you lie down, but maybe try to read something relaxing before bed?
Also, maybe your W's conversation with your D won't be as bad as you're picturing it. After all, it's her daughter, and she loves her, so I doubt she'll say something traumatizing. I think it's good that she explains what is happening to the girl, and that it would be good for you to be there. I would not drink any alcohol prior to the meeting or any time you're taking meds.
Good luck. I have you in my prayers.