Whether or not he is changing is irrelevant if you are separating for the right reasons. If you aren't using the idea of separation as a way to cause him to change, then, as I said, it's all irrelevant.
If you have decided to separate, then separate. You are never going to get any clarity while you are living with this guy. You NEED to have that separation so you can get out of the fog. This should be something you are doing for yourself and your son.