This was partially, of course, because I am an idiot.
As it turns out, Hulu videos have a "full screen" mode, which does correctly scale the video to the browser size. So I am able to get the video to fit to my screen without needing to zoom out more.
However, there is still another small issue, although this one has to do with the Playstation itself, I suspect. When I pause a video in Hulu, it continues to buffer content up to some amount, and displays a large play button to resume. This works on my Mac, but on the Playstation 3, I haven't been able to resume playing after buffering occurs. The mouse cursor moves, but none of the on-screen widgets react to button clicks. Even worse, the browser controls themselves don't respond, either - I can't go back or even quit the browser. I have to hard exit back to the main menu by holding the Playstation logo button on the controller (what is the name for that button, anyway?).
I don't know if things are getting backed up on the PS3 while doing the buffering or what, but this means I have to watch an entire Hulu show without stopping, which is a bit suboptimal. So, one hurdle overcome, another hurdle encountered.