I just binge watched the show last week. I'm fairly certain he always crushed the pills with mortar and pestle, then snorted it. As for the girl, she was his middle woman, and it was only them doing MDMA that one night. Not for nothing but that's not terribly far-fetched. I've had a girl offer me MDMA before.
MS Contin pills are very waxy. Snorting them would be a terrible way to use; he'd literally be better off with IV. I don't think it increases BA anyways.
Also, he has an attractive drug dealer girl that just comes over to give him free drugs and screw him? I'm sure this happens. But I doubt it's remotely representative to say that happens to introverted semiautistic "hackers".