Oh my....I'm so sorry. I went through a similar situation with my daughter when she turned 18. As much as it hurts...it sounds like you're doing the right thing.
Can you check your local churches, counseling centers and even your hospitals. There is usually a group for parents in your situation....google under "tough love". It's always helpful to have others to speak to who have been or are in similar situations.
Take care of yourself...hug your babies and have faith. If you need to talk...feel free to pm me.
Kim