I am so sorry.... what a terribly horrible situation.
First of all, please stop beating yourself up. True, he needs help; and true, you may very well be all he has left. But the truth of the matter is that you had no way of knowing any of this was going to happen. You did the right thing by trying to get away from him. I commend you for trying to take care of him in his hour of need, but just remember that he got himself into this situation. Even if he was not trafficking as the charges say, he was clearly involved in something that should not have happened... this, just like anything else that happens to an addict, is his own fault.
Secondly, I know I sound like I have no heart. Let me assure you that I find myself pitying my sister, who is my addict, more than I care to discuss, because it puts me back into a depression. But why is it fair that you should beat yourself up over his choices?
Remember the three C's: you didn't cause it, you can't cure it, you can't control it.
Even in regards to the doctor's visits, there is nothing you can do if he won't go.
Please don't be offended by me saying this, but how do you know that what he told this other person about having cancer isn't more indicative of his lack of a deadly disease? How does he know that the staph infection has spread to his bloodstream if he hasn't gone to a doctor? And lastly, if he really wants to die, so that he is no longer in pain, why is he "cleaning" his wounds (which I still don't understand if the infection is beyond his control)?
I know you don't want to upset him while he is so sick, but can you talk to him, and try to give him an ultimatum? If he's not going to take care of himself by going to a doctor, why should you put anymore of your energy into helping him?
Like I said, I really don't mean to be heartless... it's just that I would hate to see you fall any farther down his path of destruction. Either way, I'm praying for you.