I use VBox when I need to use an emulator. It has (I believe) a paid feature too, but I never needed to expand what VBox is capable of, so I left it alone. I'm not sure if you could run the emulator off of the SD card, my suggestion would be to put less used apps and programs (pictures, documents, videos if you have them) on the SD card or put them into a cloud and put the emulator directly on the tablet.