I can tell you how I handled it when I was in your shoes. I told Mel to get help or get out, I would support her ONLY if her goal was sobriety but I was NOT leaving. She eventually did go to rehab.. twice. Long story short, I set boundaries that I could enforce and stood firm. The good news is my kids were spared the ugly stuff and I'm now living a drama free and serene life.
Have you seen this sticky? I would swear by it.
http://www.soberrecovery.com/forums/...l-problem.html