Ok, I'll let the Kindle overnight to charge and tomorrow try again to uninstall everything / install the update. If they all fail, I will go with Kubrick when I have 2-3 hours to spare and hope for the best.
Best case scenario, the Kindle will be in its normal state and I can still install stuff. Worst case scenario, I brick the Kindle and I'll see about replacing it in the near future (let's hope this doesn't happen).
Thank you both for all the help, you guys are great!
BTW, which one of the latest Kindles would you recommend just for reading (in case I have to replace)?