Should / can i buy anymore fish for my fish tank?

There is nothing I can say that no one else has already said. I know it sucks when you tell people about your tank on here and then they trash it, and in most cases it is uncalled for, but in your case it does. Your tank is a mess and you should completely start over. You have species that are too big, and some that WILL die if they are not in a school. There are fish-keepers and fish-havers... You are a fish-haver at this point. PLEASE return your fish and do some research before you get new ones.