Regarding you video sharing problems, you have to remember that you definitely need to have a call (audio/video) in progress for these features to properly work
If that wasn't the issue, giving us some extra info would greatly help us find what might be wrong.
Info like your system specs, for example:
What version of Skype are you running?
What is your Operating System?
What is your current video card?
Now regarding your P.S. note:
Not being able to share a local video file without a video call in progress seems to be a normal thing. Who would you be sharing it with if you are not in a video call? Now, If you need to preview it, simply use your local media player for that end.
Sharing emotions/winks/sounds work a bit differently though, mainly because we can also share them through a regular chat conversation in which there is no need for a video display. So that's mainly why the local video sharing feature only works with a call in progress.
Thanx for taking the time and posting in the forums!