Unfortunately, since your phone is running only "KitKat" you would not be able to download directly to the SD Card. If you can update the device to "Marshmallow", (which may not be possible as your device may not be capable of handling that version, but I it can't hurt to try) then you would be able to see if it will allow you to turn the SD card "Internal" vs the standard "External". That is not possible on Android versions before "Marshmallow".
If by some chance you are able to upgrade to "Marshmallow" then please do make sure you start with a blank SD card, as the changes made to the card when making it "Internal" will format the SD card (erasing any data on it) and also make it unreadable by other devices.
The only other option I...