As a recovered heroin addict, I would say that it's important that he has something to live for, however, he doesn't want to ruin your life or drag you down.

That's a tough one for me, because it holds a high personal value. You could always force detox (locking in a room for a couple weeks) or, you could get him to a clinic for methadone (not recommended). He will hate you for a bit but, he'll thank you later.

If you cut him from your life, he may feel abandoned, which could lead to depression and possible self-harm. You shouldn't feel obligated to put up with it, however, he wants you to be involved in his addiction about as much as you want to be involved in it.

I apologise for rambling, simply trying to help.