You need to aproach him on a level playing field, or on an equal level of respect. Pretend putting yourself in his shoes when he tells stories or tries to justify what he's doing (this doesn't mean that you need to think what he is doing is right)
This might sound kinda lame, but here are my suggestions, I've been studying to be a substance abuse counselor, but have had a hard time addressing my own substance use issues, but these methods aren't from me, they're "text book"
Try using "Reflective Listening" and responses. Basically, the idea is when we listen to people, we are thinking and planning our responses while listening at the same time, so we tend to miss things or mis-understand. Reflective listening is while you are listening to your son speak, when he pauses, nod your head, reflect his body language, and briefly repeat what he said. Briefly, quickly, and don't interrupt him to do it. Reflective responses is, after he finishes speaking, you rephrase what he said to you in your own words. This is to make sure he 1) knows you heard what he said, and 2) you understand what he said. This will help with the whole "YOU JUST DONT UNDERSTAND MOM, YOU DONT KNOW ME, YOU DONT GET IT" because you will always be sure to be fully listening and understanding what he said AND making sure he knows you understood what he said.
Another thing you can try are called "3 Part Assertion Messages". It sounds lame but bear with me. Basically, you have: 1)Their action, 2) The effect of that action, and 3) How that effect makes you feel.
An example: When you run around and stop talking to me while doing things that put your life in danger, It really scares me and I can't sleep because I feel like you stopped valuing yourself and your life and I just want you to be healthy and happy.
These work because you tell him what he did, why and how it bothers you, but it does so in a non accusational, non aggressive way that will not likely get a violent response from him.
And quickly, just for the hell of it, these are basic, text book "Communication Barriers" that will make it difficult to have effective conversations with your son:
-Criticising
-Name Calling
-Diagnosing
-Praising Evaluativley
-Ordering
-Threatening
-Moralizing
-Excessive/Innapropriate Questioning
-Advising
-Diverting
-Logical Argument
-Reassuring
There is more to these, but just know this: trying to "hold hostage" him or stuff he likes, manipulation attempts (through threats to buying him stuff/being nice/flattery) to get a desired reaction, using moral or logical arguments to negate or disprove the things he is doing, or avoiding his concern ("i don't see you as a drug addict, don't think that because I dont"), and similar things will probably make him put up higher and thicker walls rather than helping.
With reassuring, you said your son said that you "only see him as a drug addict" to which you would naturally reply "no I dont!!" but, to quote the book I referenced to write this reply, "A persons ingrained opinion of themselves resists direct attempts at alteration", and being "reassuring" can often make them go harder in the other direction. A teacher told me that reassuring is what someone does when they like the idea of helping someone but does not want to actually do anything. Not saying that that is you, just offering some advice.
Instead of saying that you don't believe he is "just a druggie", ask him why he thinks you think that. Why he thinks you see him that way and what you do that makes him believe that. This will get him talking about how he really feels and will get him away from the vague answers.
Vague is poison for communication. Dont ask "Closed questions" (questions easily answered only with brief, yes or no style responses), and avoid being aggressive or submissive, aim for assertive
I hope this helps and I hope you and your son can work this out and he stays safe (and yourself)
