To be honest your flogging a dead horse. Deleting the numbers your self won’t help. He will find otherways. I know u mean well but all this needs to be done from him.
Your not controlling him at all, you just want the best for him. But he needs to want this him self. He needs to cut everyone off to do with coke. Even delete all social media accounts as u can message dealers on there.
Maybe tell him if he is serious of quitting u want proof he is trying. I use give my gf my phone on the usual days I used and my car keys, not buy any alcohol. And a few other things.