Welcome to SR.... really glad you found us and are able to share your story...
I completely understand your situation.... my only suggestion would be to get into an Al-anon meeting... take the focus off taking care of him and start working on taking care of yourself.... heavens knows you have your hands full with 4 children now.
I look forward to getting to know you better, keep posting and perhaps check out the stickies at the top of the form.