As for what you can do to help him. Well thats hard to say. If you already havent confronted him about it, do so, but in a loving caring way. He most likely will deny his drug use, but at least it will instill in his mind you know and care.
Other than that, there not much you can do. Hes going to use until he wants to stop. Its a hard thing to watch someone go down that path I know.
Things to watch out for.. Well in my experience, hardcore crank users usually become theifs. They will steal from there own family to support their habbit sadly. Also know they can get violent if they have been awake for 2-3 days. Its not always the case, but just something to keep in mind. One second they could be just fine and dandy, and then the next second something could set them off. Being awake that long messes with your mind.
Hope that helps.
-Ryan