Help

My son is 17 and i think he is addicted to synthetic pot. I don't know what to do. He is a stranger to me now. he has become mean and abusive to everyone he knows. he stole his dad's ipod and sold it. we have told him the only way we will not press charges is for him to go to rehab. I know they have to want to go but I'm so scared for him. My heart is broken. I'm scared. My husband says if he doesn't go to rehab he cannot live here anymore. How do I support my son to try to help him see his addiction but not enable him. I'm out of my mind scared. I can't function. He has a 5 year old sister and I feel like I'm not being there for her because I'm so depressed. I feel as though someone has died and I just want to crawl up in bed and sleep my life away.