Welcome, ah. I am sorry about your friend, sadly addiction affects all who love an addict. And if love could save them, not one of us would be here.
Sadly, he is on a roll and not likely to stop until the pain of using becomes greater than the fear of stopping. If he and his friends stay on the course they are on, it won't be long before the fun runs out and it becomes a darker time for him, so that alone may help. Nothing you do or don't do will make any difference, as much as you'd like to help.
You might be best to keep a safe distance, as he seems to indicate, and just let him know that you are there for him if he begins making better choices and takes "action" to do something about this. Words, no matter how well intended, are meaningless with active addicts. They cannot keep promises to themselves, let alone anyone else.
Take a read around and make yourself at home. We're here for you and we've been where you are so you are among people who understand.
Hugs