Finding a Kerr Black Holes I understand that Kerr Black Holes are purely theoretical and have not been found anywhere in the Universe. However, they are theorized for possible means of time travel.

I am attempting to prove in a research paper that controlled time travel is statistically improbable for the human species. Therefore if scientists have evidence that there does not exist a black hole within a distance of X from Earth, and it is statistically improbable for the human species to ever be able to travel a distance of X, I can rule out time travel by means of kerr black holes with a significant degree of certainty.

However, I cannot find this "X" threshold, which is why I am asking this question. Have scientists verified that there are no kerr black holes within a distance of X from earth for some X?
1) Nearly all black holes are Kerr black holes.

2) There are roughly 100 million black holes estimated in our galaxy.

3) There is a confirmed black hole about 7800 light years away.

4) There is a potential black hole about 1500 light years away.

5) It is very likely that there are black holes even closer than that, but they are difficult to detect.

Some of your assumptions are wrong, but for now the closest known potential black hole is still a pretty good distance away. Traveling that far with our current technology is impossible, and overcoming that hurdle is not trivial. Regardless, using a Kerr black hole for time travel may not be feasible anyway.