Good news and bad news for the baby turtle... The puffiness around his head and legs has gone way down, and his swollen eye is at least cracked open most of the time now. On the other hand, he's started spitting up water, and I believe he may have aspirated some. I'm not yet sure whether spitting up the water was due to some sort of internal issue, or just going overboard (unless they were soaking him instead of leaving him to get his own, I'm not sure how much water he was drinking there).
But regardless, now I'm cleaning off gunk from his mouth and nose regularly. If I do that while annoying him enough to move around, it seems to clear up his system for awhile. I'm debating whether or not I should send a message to the Rescue, because there is no way this turtle should be released right now...