I find myself feeling guilty and scared because I said something. Guilty because I told someone "outside" our circle and therefore betrayed him somehow, and scared because I'm worried he's mad. I'm also worried I messed with his recovery by saying something before he did.
If he's serious about his recovery, he has already told them about his other substance abuse. If he hadn't, now they know, and that is to his advantage. Recovery can never happen unless there is truth.
You also say you're worried he's mad at you. Are you fearful of what he might do to you, or are you worried that the anger will somehow mess with his recovery? If it's the latter, people can deal with that. If it's the former, read up on the posts on abuse. It doesn't have to be physical abuse to count as abuse.