A/N - Okay, I can tell this story will cause a lot of confusion and I admit it is quite convoluted. First of all, what I meant was that the Theory of Relativity says something along the lines of being able to slow down time at higher speeds. However, to actually travel back in time you must exceed light speed. That is not physically possible because it'd take infinite energy and zero mass.
Now, about the Terminator movies. Terminator 3 got horrible reviews from critics and viewers alike for the same reason you just mentioned. Terminators 1 and 2 were about hope, and that the future can be changed for the better. It told us that WE, as humans, were in control of our fate. When Terminator 3 came out and said, "The future cannot be changed," it betrayed the main ideal of all the Terminator movies. We don't know the effects of time travel, but in the cases of sci-fi we must accept it.
Thus, when I make the analogy of killing Hitler, we must all assume that killing Hitler prevents the Holocaust. That makes it a lot easier to see the point. If we didn't make these assumptions, then stories like this one are impossible to read.
There will not be a change in Future Kim's circumstance, since that is far too hard to write. For example, past Kim just seeing Future Kim would change Future Kim greatly, especially after her tender moment with Ron. However, for the sake of simplicity we will say that Future Kim can not be changed and will stay the way she is throughout the story, with the same memories independent of past Kim.
I do not go by the forking universe theory because it takes away a lot of dramatism of the story. I ask all readers to bear with me and accept the following:
1. There is only one universe
2. The future is changeable
3. Two Kims existing in the same time will not cause a time paradox
4. Ignore all the laws of physics and chemistry that I have broken
Basically, do the same thing as what you did when you played the awesome game Chrono Trigger. Chrono Trigger causes more Time Paradoxes than any sci-fi novel, but it's still hailed as one of the best games of all time due to its storyline. Think of this story as an internal battle between the Kims, and you will enjoy it a lot more.
On a simpler note, all will be explained about Ron in due time. I have kept the future vague and ambiguous for the reason; that way, we only know just a tad bit more than past Ron and Kim. When future Kim sees it fit to tell her story, then we will all know what Ron did. However, only Ron can know why and how and when he did it.