I am happy you are coming to terms with the reality of the situation and that you are playing the tape forward and realizing that you can have a life where you feel free and not anchored to an active addict.
While it might be difficult to raise your DS and run the house without your AW, I truly believe that in the long run it will be a lot easier to just run the house on your own without all the worries that come with having an active addict in the house. Also, your DS might be upset for the short term about the divorce, but the pain from a divorce compared to the pain of a lifetime living with an active addict are not comparable.
In the end you need to do what you believe is best for YOU and your DS and I think each day you get closer and closer to deciding exactly what you want.