I believe gouramis like floating plants. I recommend something like brazilian pennywort.
If you can QT the cory, you can use Melafix. Pemafix and Maracyn would also work. I suggest using Melafix or Pemafix though because Maracyn is very strong stuff. Melafix is quite common so I bet you could you could find some where you live.
As for sexing Dwarf Gouramis, the females are usually so dull in color they are almost just plain grey, with small hints of color. Many stores just sell males because nobody wants the females unless they are breeding them