The future is far more vast than the past.

[citation needed]

You can travel forward in time, that's easy. Just wear a space suit that's resistant to all the dangerous effects of a black hole, then travel towards a black hole.

You don't even need to do that. By your definition you are already travelling forward in time, which is true. You're talking about going forward at a different relative speed.

Time cannot reverse. The closest time can get to reversing, is stopping entirely. It cannot go beyond that.

You're going to need to present some pretty incredible proof on this one as physics actually disagrees with you. Despite the fact that nobody has observed time going in reverse (would they even know?) there is no law which says it cannot happen.

Time is linear, it moves forward.

See above.

If somebody from the future ever went back in time to stop a tragic event from happening, that tragic event would have never happened in the first place. You cannot "undo" time that has already passed. you cannot revisit it again. You can only skip ahead.

I'm curious as to how you've determined this to be undeniable fact, despite MWI. Are you saying that you have rules out MWI completely? If so there are some very smart people who would like to see your work.

Summary: I think you have the beginnings of a good book but nothing you said is actually grounded in math or physics.