I would definitely sit your wife down and remind her that you only have one life. This life is not just about the son who chooses to destroy his, but it is your lives as well. He has to want help/change. If he is willing to go for treatment, great. If not, it is time to draw your boundaries and stick to them.
My husband was in the same exact place as you are right now. He told me he just couldn't live like this anymore and at the time I was so wrapped up in my daughter that I thought it was my job to be on her side, to be her "protector". I thought he was a complete a hole for feeling the way he did. Only after coming here/reading other's stories, talking to my ex-addict brother and watching shows about the topic did I learn he was right and what I was doing was sooo wrong. I kept preventing bottom from coming every single time I rescued her - from anything. And I did, a lot. I don't think she has hit bottom yet, surprisingly, but the rest of the house is no longer suffering on a daily basis. We are no longer held hostage to her mood swings. I don't have to watch her come home and crash, only to wake up, eat everything in the kitchen and watch her go out and do it all over again. My house is full of love and peace now. Sure, she comes by to visit (and I can tell you that the energy instantly changes when she is here), but it is back to peaceful when she leaves. Right now, she is homeless with her boyfriend but that is a result of her choices, not mine. I paid for rehab/sober living - she left. I would pay for rehab and sober living again, but nothing else (besides the cell phone so I know that she is alive...).
Your wife needs to come to this site, or watch Intervention/Rehab with Dr. Drew, attend Al Anon - something. If nothing changes, nothing changes. But let her make that decision. Don't just leave. Sit her down for a long talk first, let her know how you feel and where you are at. Either she joins you in therapy or you need to do what is best for you...