Hbird, I have had fantasies of leaving the house temporarily just to avoid my son and all of his problems from drinking. I stop myself because my husband handles it quite well and it really wouldn't be fair. However, if I knew my son was going to be gone soon, and I received no help from my spouse, I'd be outta here in a heartbeat! Yes, it costs money but to save my sanity it would be so worth it.
I agree, your son is working hard in school, and seems to have a goal in mind. This is a plus. My son was like that once but the liquor completely derailed him.

I think this could definitely backfire. My exABF's mother did all she could to protect me and to help her son. But, with my codependence issues and his alcoholism, it just became a bad scene for all three of us. I can honestly say that she did identify her own Codi issues, which is why she was so engaged in our relationship- that and her actual love and respect for the both of us. But, I regret engaging with her in such an intimate way about my relationship with her son. I believe that if we had both had better and healthier boundaries, it would have led to very different outcomes in our relationship (me and my ex's mom that is...)
Unless you are preparing for an intervention, I am not sure that reaching out to her would help. Maybe she will come to you (like I did with my ex's mom, but even then- heed the warning- there are certain lines in relationships that must be respected if you are to survive all of this in tact). I also would not post something on Facebook about your son. That is a very public place for such a personal issue...that could push him away from you.