First of all, don't take any xanax. Then you'll be doing exactly what he's doing...numbing your feelings as a way to avoid them. It doesn't work.
I'm a recovering addict and a recovering codie. I think you, absolutely, did the right thing in telling him to get help or get out. He's 23 and old enough to face consequences of his using.
I also don't exactly believe that you pressuring him about drugs "triggers" him. When I got into recovery, my dad was always asking me if I was craving drugs. I'd tell him "gee thanks, dad, wasn't even THINKING about them 'til you brought it up!", but it never made me want to use. It was more of an annoyance. He didn't have to ask me long, though, because my ACTIONS showed him I was not using.
Do you go to al-anon or nar-anon? I think it would help you a lot to get some f2f support, although you will get lots of it here, too.
He's going to do what he's going to do...in your house, with a friend, in treatment. The best thing you can do is focus on you, and let him find his own way. If my family hadn't let me fall on my face, I would still be using, not with 18 months of recovery.
Hugs and prayers!
Amy