Good Morning Hummingbird,
I just wrote a long reply, but had to delete it after I read your most recent post.
You've clearly got two problems that you're trying to deal with. 1) Your son's addiction, and 2) Your family's attitude toward it. Forget what's happening outside with the weather. You've got the perfect storm happening inside your house!
My hunch is that you're going to have to learn to be very clear and concise with how you communicate to both your son and your family. Being sure to use only "I statements", stuff like that. I'm sure your therapist has talked to you about this. Detach, Detach, Detach. Boundaries, Boundaries, Boundaries. When I first started learning better communication techniques I started seeing an improvement in my own situation. It didn't keep my STBXAH from drinking, but it kept the chaos down, and therefore allowed me to make calmer choices.
It's great that you have a therapist, and even better that you've decide to go to Alanon. You need to be around people that can support you. Especially since you're not getting that support at home.
(((((((( hugs )))))))))