I'm a real wet blanket when it comes to pet time travel theories, mainly because I've been in so many threads like these, where people who don't know a damn thing about anything come out with their fifth-grade knowledge of E=mc^2 or some other scientific factoid and try to turn it into a functional scientific theory...and it just blows my bagpipes. Sure, it was fun the first zillion times, but I can only swallow so much "Oh, gee, if you go at the speed of light through a black hole, you have infinite energy, and zero mass, and blah blah blah."
You've opened a can of worms, my friend, a real can of worms!
Addendum: On a slightly less caustic note, the only time travel model I have ever come across that had no apparent logical flaws, was Barrington Bayley's "nodal time" model. He wrote several short books which you may want to check out on some slow and rainy day, including one called Fall of Chronopolis.