His choices are his. He can choose who he hangs around with. Even if he's hanging around with addicts, it is his choice what he does. You don't have any real control over it. He is a grown man. It is not our place to decide who our As friends are. It is not our place to tell them what to do and where to go. It is all up to them. We have to allow them their own power to make choices and to face the consequences that go along with those choices.
As far as second guessing ourselves, I was the queen of that. I decided that I was always afraid of making a mistake - that's why I could never make a decision. I also decided that it was perfectly OK to make a mistake. Everyone does it. It's not the end of the world.
Hugs - L