The stability of debian is based upon their conservative approach to software, they take a while to test software before pushing the updates which is why they are known for their stability. Up-to-date software will only limit the stability.

I did check distrowatch for debian testing based distros at (http://distrowatch.com/search.php?ostype=All&category=All&origin=All&basedon=Debian+%28Testing%29&notbasedon=None&desktop=All&architecture=All&status=Active) and found that antix and pardus are based off of debian testing, I have heard good things about both of those but have not tested them myself.

You can try Siduction which is based upon debian sid, one of the mods here is a core member of the dev team for that distro.

I apologize, but as far as I know there are no active kernel developers on this site. I highly recommend checking out http://kernelnewbies.org/ , there are many helpful people on their mailing-list that can point you in the right direction.

Fortunately QT is quite well documented, you can find guides for all elements at http://qt-project.org/doc/qt-4.8/tutorials.html

If I understand which app you are using, then it would be youtube-dl which is a command line app. This may present an issue with your difficulty with the command line, but that pp is rather easy to use for basic needs however you must understand that not all videos are donwloadable. The basic use of the program is typing the command name "youtube-dl" followed by pasting the address of the file you want to download. You can view the other option by typing "youtube-dl --help", however I have not yet found a need to use any of the options.

There are alternatives such as gnash, however they generally lag behind the official version's features because they are best effort. However you can try to install google-chrome which includes it's own internal version of flash that is developed by adobe and google.

You can remove adobe flash as you would any other application in your package management tool.