If his pain was legit, the doctor would prescribe him painkillers. Strong narcotics aren't meant just for mediocre pain or emotional pain (although I used them that way as well, and found out they actually do more damage than good - who'd a thunk it?)
He's playing the blame game so well, from what I read, that even he is buying his own bullcrap. What raises a red flag is how he turned your concern about him touching your medicine, into a "woe is me" production - this says it's all about him.
"When the pain of change is less than the pain of staying the same, change will come" - your boyfriend won't change as long as you keep giving him your medication. While giving into his demands is easier in the short term, it's destructive in the long-term, and you're enabling him. I played the 'woe is me' act with my mom who gets a prescription, and I'm pretty sure I whined about every ache imaginable - hangover headaches, my recovered broken ankle which would continue to hurt for forever, etc. She would complain about giving it to me, but she'd still give in. I took advantage of that fact until I entered recovery.
Prayers for your Dad - I hope he gets better soon.