I'm sorry you're still going thru all of the heartache of loving a substance abuser and having a troubled step son (who is also a substance abuser). I've wondered how you've been faring.
For many of us here, we have to hit our own "rock bottom" the same as our kids or loved ones who are mentally ill or addicts. Once we, as enablers, hit that bottom, it is usually the beginning of change. As is often said around here, nothing changes until something changes. You've been living on hope that others will change, it's a desperate place to be, we have no control over others, all you can do is learn to respond differently, let go, detach from their behaviors and choices and accept what you can't change. Remember, the definition of insanity is doing the same thing over and over and expecting different results.
Your wife and her son have a dysfunctional relationship and all of you are in a broken family system. Without acknowledgement of the issues, nothing will change. Perhaps in Rehab your wife will learn about how her addiction keeps the broken system going. Maybe not. However, whatever your wife decides to do, however your step son behaves, you must find a way to take care of you. We used to say in the 60's, if you aren't part of the solution, then you are part of the problem. You're part of the broken system. Find your way out, either by actually leaving, or by stopping your enabling of your wife and step son. Learn about boundaries to take care of yourself. You appear to be the scape goat in the broken system. Get yourself out of that role, one way or the other.
I know how hard this is. Take care of YOU now.