Mac iTunes rewind key shortcut

It seems that iTunes only has a keyboard shortcut to rewind to the beginning of the song but I would like to have the option to jump back 5 seconds or so.

Now I found this: http://www.dougscripts.com/itunes/scripts/scripts02.php
I installed this script and it shows up in the iTunes menubar. So far so good.
However I would like to know if it would be possible to assign a custom shortcut to this?

And while I’m at it: could I also change existing shortcuts like F9 for the actionscript panel in Flash? 'cause when I hit it the first time on my new Mac… whoops surprise… all of my opened windows move to a corner of the screen.
Also quite nice, but not what I would like when I’m working in Flash.

Cheers.