This is my last comment. :-)
You obviously can't trust him because he lies. He didn't TELL you until you CAUGHT him. That's not trustworthy behavior. That's dishonest.
A guiding principal when it comes to dealing with addicts is: Hands off the addict. I know you have heard this a million times.
Focus on med school ;-). And let him focus on his own recovery. he seems to have it under control, right?