Sweetheart you need far more help than anyone on here can give you. Your boyfriend needs to see a therapist who can help him deal with his anxieties and insecurities, and feelings of failure. He has to be made to realize that he can't blame himself for his brother's behavior and past activities. And he is not responsible for his parents financial difficulties related to his brother's illegal actions. If his parents have wasted all their money trying to bail their irresponsible son out of his jams, that is their problem, not John's, and he shouldn't feel obligated to bail them out. As you yourself stated, John cannot save the world and he has to come to that realization before it destroys him. Guilt is one of the hardest feelings to deal with and he should have no reason to feel guilty for something over which he has not contributed, nor is responsible or has any control to change. His brother IS the PROBLEM, and is destroying the whole family with his actions.
Try your hardest to talk him into seeing a professional, for his sake and all those involved it is necessary! Good luck, you're going to need a lot of it, if you plan to stay with this guy and this myraid of problems.