As for T2. It doesn't matter which version you see, they still kill Miles, blow up Skynet and destroy all of the Terminator chips. Therefore, logically, how can the machines rise? All traces of them have been destroyed. The only logical way for this to happen is if someone went back in time to before Miles was killed and stole the chip that Skynet had from the original Terminator. Now if that happened, then maybe, I could buy the story of T3. However, by traveling back in time to steal the original Terminator chip then that pretty much negates the events of T2. Sarrah's whole quest to stop Skynet in T2 becomes a mute point.
Also by your logic, if the future is unchangable, then why did they send the Terminator back in time to kill Sarah in the first place? If the future is unchangable then with or without Kyle's involvement or the Terminator's, John was going to be born and therefore become the leader of the human resistance. It didn't matter how many Terminator's went back in time to kill Sarrah or John, they were going to live to fulfill their destiny.
The future is the past. The past is the future. The whole thing gives me a headache.