Being clean and sober is quite an accomplishment.
I know this has to be hard accept now that he's doing well, but there are treatments for Hep C, and given he is no longer using, I imagine he's a good candidate.
There's often the "aftermath" to experience when you are dealing with addiction. This is something that although difficult to swallow, is manageable, as long as he is willing. Meetings will help him, as Hep C is not that unheard of with addicts.
Hang in there, you and he are in my prayers.
(((Hugs)))