Your son is right, and it sounds like you have been a great mom in the past for him to be able to make those decisions on his own. With him gone it's going to be even harder for you to kick ABF, but in your heart you know you are riding a painful merry-go-round that isn't going to stop until you leave the park.
Maybe this will be your bottom. If you can find the courage to discuss this candidly here and admit the painful truth you can find the courage to leave the A. Staying has only made everyone's situation worse. So sorry for you and your son. Be strong.