he is not looking for a job and is not interested in doing so
Maybe your boyfriend doesn't quite intend to say this, but what he expects is for you to be quite happy on to carry on as you are, maybe forever. Think about that. No shared house, no children (most likely at this rate) and you being a carer for him for the rest of his days whilst he smokes weed. I wonder why there's tension in his house. I wonder why he still hasn't introduced you to his family yet. Could it be that you are a good enough for now type of girlfriend, and therefore doesn't want to introduce you because he knows he will then be held even more accountable for his current situation than he already is?
To expect you to put up with that is just a recipe for disrespect. There may be times when someone doesn't want to emotionally let go, and other people will be really grateful that you stood by them through thick & thin. I think you're hoping for the later....but I'm afraid so often it doesn't result in more devotion or respect. In fact quite the opposite. You have shown exactly how much you're willing to put up with....so next time he might get confidence that you'll put up with more.
Maybe you feel like you're abandoning him if you leave. It tugs at your heart, at your 'what if' insecurities, but you know what. He is not a child. Literally. I want you to really take that in - he is an adult male, NOT my child. He is not your patient either and even with patients, there is only so much anyone can do if they don't want to help themselves. It's hard, but sometimes you just have to accept that nothing will chance.
At this time in your life, you are at a very crucial stage. You have a good change of meeting someone, a good chance of setting up a home and having children maybe. Please, please don't throw those chances away because you feel obligated to be someone's carer in anything but name.