Keyboard short cut to skip back 5-10 seconds in iTunes TV show?
I would assume that this is possible using AppleScript, and when it comes to AppleScript and iTunes, DougScripts.com is always the place that I check first, which led me to this:

Skip Back or Ahead: https://dougscripts.com/itunes/scripts/ss.php?sp=skipbackorahead

I don't know if his scripts control video as well as audio, but if they don't, I bet he'd know how to adapt it.