Chris, you can (and must) leave. You know this.
We realise it's hard, a HUGE thing to do, but you can't help her, only SHE can help herself.
Your son is suffering, YOU are suffering.
If you stay, somehow it will support the status quo, and all the while your son is living with an addict. the older he gets, the more it will affect him.
Please go and talk to your GP, your health visitor, and find out who can support you and your son in this.
angelintraining - how naive you are. You are advocating he stay involved with an addict because it may upset her if the child is taken by his father?
WELL THEN SHE NEEDS TO SERIOUSLY REVIEW HER DRUG USE THEN DOESN'T SHE?
Sorry for shouting, but the mother is making a choice to smoke weed. It may be psychologically addictive, but biologically it can be stopped easier than nicotine.
the ONLY way this woman will get help is if she asks for it, and to do that she has to see what her actions have caused.
She is like an alcoholic, she needs to hit rock bottom to see what she is doing. There are plenty of people there to support her should she choose to let them but if she doesn't want to stop, she won't. She will drag the whole family to hell for the price of a spliff without a second thought.
Chris should absolutely NOT provide emotional support to his wife when he leaves. He needs to focus on his son, himself and their future.