King is looking much better today. His color hasn't completely returned yet, but his fins are opening up again! There still appears to be a bit of gray at the tips of his dorsal fin, but there haven't been any fin bits in his bowl for the last day and a half or so. He's eating normally again and swimming all around his bowl.
I'm hopeful that I won't end up having to use the kanaplex that I bought and that he'll recover on his own. I'm currently doing water changes every other day as to not stress him out too much.
Just curious... I've read all over the place that you should stop aquarium salt treatment after 10 days. Why is this? What if he isn't 100% recovered after 10 days? Will it hurt him to keep him on it longer? It seems like some people have aquarium salt in their water at all times.
If it is necessary to take him off the salt after 10 days and he isn't better, how long do I have to wait before treating him with it again? It has been only about 6 days, but I'm not convinced he'll be completely healthy in 4 days.
Here are some pictures from today.
His pectoral fins are completely open again, which is a relief. His new tank should be here in a day or two, though I'm going to hold off on moving him into it until I'm convinced that he's at least 90% better and I get a filter.
Anyway, thank you so much to everyone who has helped me out. I owe King's probable survival to all of you.