I haven't commented because I kinda felt the important points had been covered but I also think something obvious is being missed here.

The guy is a drug addict, and as such his behaviour is always going to be selfish and single minded and unpredictable and probably illogical.

For the record I am a long-term functioning addict (24 years)

It is in our nature to be secretive and deceptive because we have to be to get away with what are doing. Even if it's just lying to get a job. Or lying to keep a partner, we all do it and it's easy for that to spill over into our everyday lives.

It doesn't surprise me at all that he is incredibly secretive yet jealous at the same time. You get like that when your constantly hiding something, you expect others to be doing the same.

And anyone who claims cannabis isn't harmful needs to spend sometime in the local psyche wards. The strength has quadrupled in the last10 years and certainly in the UK is the cause of a large number of psychotic breaks in teenagers.
Also start mixing it with alcohol and you have a whole different issue.
The OP made some mention of his behavior when he was waiting for his gear and that straight away sent alarm bells going.
He already seems to have some unpleasant character flaws and I can almost guarantee he doesn't think he has a problem. But there is a particular type of self righteousness with these type of people when they don't actually believe what they are doing is wrong or has any effect on others.

Anyway just my 2cents.

Hope the OP has the strength to walk away, because the only things I suspect he really cares about, are his habit, and his ego.