Hi Marie,
I am currently in a very similar situation! Reading your post was a bit like reading a diary.. weird!
I too am madly in love with my boyfriend, we have been together for 3 and a half years. He too smokes a lot of weed and always has done.. I have tried to accept that this is just who he is and tried to get past it, and he’s actually very lovely when he’s high! But I know that it creates other issues for him when he’s not high such as lack of motivation and paranoia.. so its a tough one.
My boyfriend too gets angry when I try and help him cut down on weed and I too am only doing this through love! He also has issues with jealousy and is very possessive over me, I’m not sure where this comes from but its deep rooted insecurities for sure.
Our relationship on the whole is a very healthy happy one, I’ve never been happier with a partner! But the arguments (like yours) get waaaaay out of hand and it has often made me question whether he is the one for me. The feeling I get when he’s angry is just the worst thing ever and I can’t bare it. I often wake up the next day and try and pretend it never happened to get back to the ‘happy’ us.. which of course isn’t healthy as its not resolving anything and these blow out arguments will keep occurring.

What I have come to realise is that we will never work unless he realises and admits that he has a problem. I am currently trying to rally his friends and family around him to try and make him see that its his own issues that make him paranoid, jealous and angry and not me! He sometimes really believes that its me and its very difficult to make him see that its his own insecurities. So.. I think, unless you want a lifetime of these same problems occurring, your boyfriend needs to realise he has a problem, and that is the first step towards change. Unless he can do that, things will stay this way. And unfortunately, he has to do this himself.. us trying to make them see they have a problem only pushes them away and makes them angry and defensive. Its out of our control which is the saddest part.
One word of advice, never feel like it is your responsibly or that its your fault that he is behaving like this. I know that sometimes you can question whether its you that makes him behave this way. It isn’t. Stay true to yourself and know that you are doing everything you can, the ball is in his court now if he wants to keep you.