I recommend focusing on dream control rather than on preventing false awakenings. If you can change your dream to make it no longer scary, then not only have you stopped a nightmare, you also have a pleasant lucid dream to enjoy. If you manage to change a nightmare into a non-nightmare even once, that might be enough to stop them entirely; I've heard reports of recurring nightmares stopping after the person having them defeated them or made them not scary just once. For improving your dream control, I recommend Mzzkc's threads on the topic.