Rescued Irridescent Shark

[youknowit194]

For some reason I was in Petco the other day and took a look into the rescue tank and there was about a 10 inch long iridescent shark. One eye is swollen and covered in a white film and it has ich because they put it in a tank with all other fish that have ich. I bought the fish thinking that I would put it in my 55 gallon and try to nurse it back to health but that did not work out as my parents are moving and wont let me set up the 55 gallon. Right now I have it in my 20 gallon hospital tank and I feel horrible. It constantly looks like it is trying to get out of the tank and has marks around his mouth as well as ich and his eye problem. His eye is now red underneath and the white film is coming off. At a local pet store they recommended maracyn-tc and coppersafe. I have also been using epsom salt, about one tablespoon per 5 gallons. Is this right or should i be doing something else. I feel horrible that he is in this tank but if he can make it through a few weeks in this tank he will go in the 55. Please help!