Hmm... yeh, sounds plaussible. I only thought that, somehow, time repeats itself (?) and some stuff happens again and again and others not. So I suppose that Archer was the Shirou from another loop while this Shirou dones't necessarily have to do the same stuff. Of course, I don't have any basis for this theory, just some ideas.
This same paradox is used in various other series, Terminator and Ever17 are prime examples.
Yea, but thats why I don't think its even possible to travel through time. Even if you could, it wouldn't make a difference as all of time is set in stone and the notion of free will is an illusion. If you could travel through time, time would have to be written already. If time is written already, then time already knew about you going back in time or forward in time, and all of the changes you may make were already written into the original plan and as such, a paradox doesn't exist and nothing changes. I merely think that time travel is impossible no matter how you look at it.