That sounds like a really tough situation. I want to echo grewupinabarn--it's really great that you're thinking about how to care for yourself in this situation. How can you get the support that you need for yourself and for your son? Something that sometimes helps me when I get into that ACOA trap of thinking about how people or situations are totally dependent on me, or I'm solely responsible for something overwhelming is to visualize my "team." For example, the parent support groups that you attend are definitely part of your team! Are there others who do/can help you with advocacy, or exploring your options, or caring for your son? Alternately, I sometimes make lists of what parts of a situation aren't my responsibility--what (it doesn't matter how small) can you pass to him or to others?
Keep up the good work!