It's always so sad to hear when someone has put together so much time resorts to using again. I will never understand the addictive mind. My exhusband is also a crack addict. It still kills me to know that he still walks down that road.
Whether you stay or go...start by taking care of you and focusing on your needs....do the things that you need to do rather than focusing on his addiction....I know how crazy it sounds...I mean how can you not focus on his addiction when it smacks you in the face everyday but it is possible when you put effort into it. After a while it becomes more effortless and your mind becomes clearer for you to make the decisions you need to make. Define some boundaries that you can hold yourself to.