Hi Blouise,
im sorry to hear about the struggles with your son at the moment. There is a lot of mums on this forum that are in similar situations and are very supportive. I am an addict and currently still smoke cannabis as it helps with keeping me away from everything else.
Is your son smoking weed everyday? If he is, can he afford to buy it daily on the wage of a part time job? I dont mean in anyway to scare you but teenagers that smoke weed are exactly the type of person drug dealers are looking to recruit to do their dirty work. Like i say my intention isnt to scare you but just to make you aware (if you werent already).
im sure some of the mums on here will reply to your post with some mother to mother advice if theres anything i can try and give you an insight into from a users perspective that you could use when you are able to speak with him then im more than happy to answer any questions.
I wish you all the best.