Well, 'End Watch' is indeed a true story. It might have some fictional elements added for the sake of entertainment, but at its core, it is rooted in real happenings. This makes it more interesting as it gives a glimpse into the real world situations that inspired it.
Hard to say. Sometimes stories like Fire Watch draw inspiration from real-life but have fictional elements mixed in. You'd have to do some research to find out for sure.
I'm not sure specifically which 'the watch true story' you are referring to. It could be about a real - life event related to a watch, perhaps a historical watch, a lost and found story of a precious watch, or something related to a particular person's experience with a watch.