My daughter was diagnosed at 13, so I know exactly what you're going through and feeling. Esp. the helpless part.
I can't really comment on the blood transfusion, as no experience there. Has he been passing blood for some time? Sometime when inflammatiion is present for a long time, the tissues weep blood, and over time levels start to drop.
He will likely continue on the steroid, (Prednisone), for 8-10 weeks, but he should be starting to feel better very soon.
I'm sure you'll get alot of advise here, keep posting your questions, there is a wealth of knowledge and experience on this forum.