(((BeachyBabe))) - I don't think you're overreacting, at all. From what it sounds like, unless he's in a structured enviroment (rehab) he hasn't been doing much recovery at all.
Being stoned, all the time, is setting up a really bad role model for your girls. Add that to the angst YOU are going through, and I'm pretty sure they feel the tension. Not blaming you for your feelings (which I understand well), just pointing out how perceptive kids are, and that age, if there is anything going wrong, they often feel they are to blame.
You've found a great source of recovery, ES& (experiences, strenght, and hope- from peole who "get" what you're going thoug.
Hugs and prayers,
Amy