I wouldnt worry too much about people downloading your vid and claiming it as their own work. What can they gain and what can you lose?
Stick a watermark on it, and hope most people enjoy looking at and get somthing out of your work!
As far as the scene file goes if youre that bothered about it then dont make it available.
I can sort of see your point about months of work etc, but do you think this place (and many others) would develop like it has if we didnt share our ideas and work?
dont want to sound like I'm preaching.. just offering a different perspective