1) Bending time-space into a loop? Wouldn't that just result in everything being repeated over and over and over again?
2) As pretty much everyone has said already, the impact of altering the past, even though if you shot your grandfather before your parents were born, that doesn't mean that your grandmother didn't have children with someone else, therefore you could still possibly exist, just as a completely different person.
3) It's too confusing
IMO, just leave time and space and all that sci-fi stuff the way it is, get over how crap your life may be, because, more than likely, it'll be even crappier if you go messing with history
Think about it like this, what would happen if some person went back in time and changed it so the civil war never happened? If Lincoln didn't sign the Amminsapation Proclamation (Sorry for bad spelling) we would prolly have African American slaves. That's not cool in my book.
I've thought of something. I realize that time travel is way more than a simple math problem, but, what if this formula could help?
c = dy (Current Date = Day you want to arrive in what year)
Make sense to anyone else or do I need to explain more?