30fps seems like a bit of a specific framerate. Are you sure you screen isn't set to 30Hz, either in the FF display settings itself if that is set to "fullscreen", or in the Windows monitor settings if FF display settings is set to "borderless windowed". If that is set to 60 (or higher), maybe your fps is capped to half/quarter rate at the bottom of the FF display settings? Or double check the Nvidia control panel for a framerate cap, either globally or in the FF profile.