I would like to gently encourage you to reframe your thinking.
You say that you have been through hell because of his drug use? So when you say you worry about "losing him" that, to me, is a red flag. It should not be a matter of losing him. It should be him losing you. You should be establishing firm boundaries and making a commitment to yourself that you will not, under any circumstances, allow him to put you through this hell again.
Also, the fact that you call him "newly recovered"- another red flag. He is IN recovery, and will be for the rest of his life. I'm sorry if I seem to be nit-picking little nuances, but a lot of this sounds similar to my old way of thinking. My ex did went to rehab, which at the time, I thought was the magic bullet. It wasn't, and he has certainly not recovered.
Please put yourself first and allow him to do the same. Trust in fate, or your higher power, that things will work out exactly as they should.
I was terrified of losing my ex. Moreso to another woman than drugs. But in the end he lost me. Now he gets to continue to experience this hell and I am free- and happier than ever.
Blessings and peace to you.