So, your entire argument is based on a movie about speculation about what could happen if we were able to go back in time?
Discussing speculation about something no one knows, no one at all, and, frankly, material that is impossible to know, is futile, and will yield nothing.
The thing you're talking about is referred to as a temporal paradox, and if you researched it far enough, you'd understand what I mean. The grandfather effect is just about the same as the butterfly effect. Pure speculation that likely will never be proven/dis-proven.