Given the circumstances that I have no idea who he is, I would first try and take him in and nurse him back to health after learning of the situation. Make sure he cleans himself daily, cook 3 nutrient filled meals a day, and prevent him from self harming. I'd attempt to get him into a routine so he can be self sustaining.
From there, I'd attempt to help him finish school with passing grades while keeping him in a well managed environment. From here, he would be able to experiment and do things for himself. The possibility of dating is never out of the question, and desu he seems like good boyfriend material.