It sounds a lot like ick. You've already tried the methods I know so I'm sure someone wit more experience will help.
About the fin ripping: do you have any sharp decor or gravel in the tank? He might have ripped it on that. He might also be tail biting. It will grow back in a short while and you will see clear growth to show that it is growing. If it is black and looks like it is rotting, it is fin rot. You should treat that with aq salt.
Edit: Homegrown terror, My laptop did not show your post until after I posted. It's done that twice now
. Sorry if I repeated some of the things you had said