He chose not to get to judge on whether you take antidepressants or not, when he walked out. That's your decision to make.
Be kind to yourself. Try to have a good sleep, if you can (the alcohol may or may not help, there, but steer clear of any more or else you'll feel truly shite) and get yourself ready to use the weekend more constructively, if you can. Try not to waste your emotional energy on begging texts - whatever his actual reason for leaving, whether your fault or not, they won't change his mind, unfortunately.
One thing to focus on is to be prepared for what may come. Make sure you can access all your financial details, accounts, insurance policies, loans etc and get copies of all of his, too, if he's left anything behind.
And maintain the conversation about your DD's - they're plainly hurting as much as you and DD1 obviously feels very angry with him and probably feels utterly abandoned.
But yes, we have no idea whether he was justified in leaving or not - I suspect you're being rather hard on yourself - but even if you'd been utterly awful, it's still very raw and painful for you 
Oh, and take the tablets. You don't even have to mention them to him. They take a few weeks to kick in, so there will be no sudden dramatic changes in your personality that you'll feel forced to explain.