Lairswife this is such a shame. I hate to think what damage he is doing to his digestive track. You've already done all that you can do for him, now he has to decide if he wants to continue living out of his car, swallowing huge amounts of this drug or pick himself up and reach out for help, find a program or meetings. His choices....his consequences. I know it's not easy. He seems to be in complete denial, doesn't think spending $400 a day in Imodium tabs is a huge problem then there isn't anything you can say or do to open his eyes.
I think going on with your life, taking care of yourself and your son, are the best you can do under the circumstances. Keep reading and posting and know that you are not alone.