D's steroids seem to have done the trick. The swelling is gone, the rash is gone, the fevers are gone. He's a bit hyper, though. Well, a lot hyper, really, but only for a couple hours at a time.
He's still on the steroids, and we'll wean him off over the next week. If no rash or swelling comes back, he'll get the "all clear."
I don't know if I should be worried about the little baby mustache he's growing, and I feel a little guilty that his batting average has gone way up since he started his steroid treatments . . .