Well which is it? The universe is either causal, or it is not.
btw, If you run your sig video backwards, the ice cream bars are manufacturing the machine.
I believe what you are implying, is that in order to time-travel, you need to reverse time.
That would not be the case. Time always goes forward, not back. When you are traveling back through time, what you are really doing is to go forward in your own time, in order to enter a portal that leads to a past light-cone. During this process you are moving in a continually forward direction that leads to a "fork" in time.
Because of time now having a separate river - nothing that you do in the past light-cone that you are visiting will effect you in whatever time you are presently in.
Even if you were to accidentally run over and kill yourself, you would still remain, unchanged, in spite of killing yourself. The difference would be that now, in this separate river of time, the younger version of yourself would cease to exist.
Bother versions of the "fork" are equally "real" and they have no baring on each other. Even if one version of the universe were to re-collapse and the other were to die a frozen death of expansion.
Hope that clears it up a bit.
Again, this is simply my personal hypotheses and is not anywhere near ready to be tested ~