After months of trying to fix my internet, I finally get it working and download Broken Steel (and the Pitt, and intent to get PL eventually). And my character finally reaches L21. But he remains the Last, Best Hope of Humanity. Level 22, he's the Last, Best Hope of Humanity. And so on. Aren't I supposed to get new titles when I start in on Broken Steel? Is this a bug, or is it a unique aspect of the PS3 version of the game?

Yeah that's a bug there are new titles with Broken Steel. You might want to check here for this bug. http://fallout.wikia.com/wiki/Fallout_Wiki