but I bet we'll have the same argument over and over.
Yes you will continue that argument over and over. His resentment will build until he removes you from being an obstacle to his choice to use drugs.
OR
You remove yourself from this relationship that frankly is going no where except to cause you further hurt, pain and disappointment.
As you said, he is a lifelong opiate addict, history doesn’t repeat it self people repeat history. He is clearly showing you who he really is and not who you want to believe he can be.