I know it wasn't about them getting together and about sacrifice or what ever, but during the movie you got to see how much they loved each other and everything he went through to make everything right for her and his family. In the end the only way he found was to make sure she wasn't in his life so she wouldn't get hurt. And at the end when they're walking away he didn't really go up to her because he didn't want to screw things up.
Evan learned his lesson. Somebody's life is going to be miserable if they're together.
Regarding the "killing yourself, you can't be dead" discussion, I believe that was what Doc in Back to the Future talked about. The paradox.
This is why I don't believe time travel can be at all possible. Say I got break up with my girlfriend for some stupid reason. I go back in time to change it, never breaking up with her. There wouldn't be a reason for me to go back in time anymore so I wouldn't have traveled back to begin with. There are loopholes with changing anything in the past, not just killing yourself. Hope that made sense.