Magiimice, would I be right in thinking that your line of reasoning is that any apparent past-directed time travel would depend on the frame of reference of the observer? If so, that, surely, is what relativity is "all about".
KG is right, we cannot change the past, because every point is an immutable spacetime event, and even the act of going to a point in the past, unless we were there originally, constitutes a change.
There are those who argue that the multiverse gets us round that difficulty, but I suspect that even the multiverse would not really solve the problem.

There never was nothing.