There are plenty of responsible mature adults who don't drink/use, and still end up losing their jobs every day.
I'm one of those. My last day at the job was November 5th, despite being told beforehand there was the possibility of "temp to hire", which was a ruse to get all the temp workers possible to clean up the mess in that department, then cut us all loose.
I don't want anyone to feel "sorry" for me. It is what it is, and life often isn't fair. I'll keep putting one foot in front of the other, and doing the next right thing.
I see you getting stuck on this "feeling sorry" for him thing more than once.
Allow him the dignity to make his own choices and live his own life, regardless of what is dished out to him. He's an adult.