Yeah, I hate the passwords too. Inexcusable oversight by the developers. Still, this is loads of fun to play!
I once managed to save every victim on every level (*ALMOST, since there is one that can't be saved), but it requires a lot of planning and even then a bit of luck. There are some places where enemies spawn right next to a victim, making it nearly impossible to save them unless you learn a few tricks.
SDA still has my run. It's over 2 hrs long and isn't necessarily done fast, but I was just going for 100% rescues (well, 99.8% as you'll see).
http://speeddemosarchive.com/Zomb...