There's nothing weird about you feeling like you're going to break down. Your situation makes you fragile. Anyone in your situation would have felt the same. We become sick being with an addict because that's not a normal way of living. It's extremely exhausting and stressful. I worried when my AH was alive, a lot, always afraid he was going to relapse, which he did.
It's okay to break down, we would get crazy if we didn't. I too believe it's a good thing that you will be on your own with the rest of the family when your AH leaves for rehab. It will give you time to feel what you're feeling, cry, shout, rest and think. You'll probably think a lot. Try to take one day at a time,or even a moment at a time and try not to think that much ( or at all) about what if he doesn't make it? What if....? Or I should or I could. It will do you no good. Those thoughts have been killing me since my AH died. If it goes south, you will make it. I thought I wouldn't when my AH died but I have because I have to, because of my son. I wouldn't call it living, only surviving since I'm terribly depressed. But you will make it no matter what, surviving day by day, moment by moment.
I'm glad you feel inspired by me because it gives you strength to know you can do it, no matter what your AH decides to do with his life.
Hugs to you