If I make a starter, then it turns out I can't brew for some reason, I can dump the starter in a sanitized mason jar, cap it and put it in the fridge for a week, right?
I wouldn't see why you can't do that as long as everything is sanitized of course. When you are ready, make a starter again since maybe a percentage of the yeasties died off.
That will work. Last time I ended up this way, I just stepped up the starter another two times, and ended up with a crazy starter by the time I brewed.