Agreeing to a "trial separation" isn't exactly caving. You're still out of the house, and everyone gets a chance to get used to the idea. You never have to go back, no matter what he does. You can continue with your own plans. Even if he gets sober, you aren't obligated to get back together with him.
I suggest you use this time to line everything up to make for a smoother exit--go ahead and see a lawyer, start gathering the necessary information. And some Al-Anon meetings wouldn't hurt, either. Even if you never go back, you've still been affected.