You do seem to have hit a really tough patch, everything happening all at once, as if it's out of control. Reading your post, you appear at the center of too many things, without help. Maybe the school will help you for part of your son's behavior there but for the rest of your situation ?
Where I live, there is a community center and it offers the services of social workers, someone who knows and understands the full circumstances of a family. This person can direct you to resources (as in therapists or psychologists or lawyers, if need be) and will meet with you on a weekly basis or speak on the phone in order to steady your footing, help you focus on things. This might help you. My employer offers this service also and although I would never speak of my family problems at work, I have used this service with confidence : it's free and if you don't "click" with the person you speak with at first, they can set you up with someone else.
Hope this helps. Best of luck,