As long as your Windows' device manager does not show the device in USB downloader mode, you don't need to bother trying to do something with ATK. You can restart ATK as often as you like but it won't work. You need to be careful to bring your K3 into USB downloader mode. By pressing Vol- during start-up. You cannot bring it into that mode by software or from the host PC.
As I see it, either you're failing to press the right button at the right moment, or your hardware is broken. I'm irritated that you're fiddling with ATK (restarts and reinstallations) rather than concentrate on your Kindle.