 
 Suggestion - in your startup splash (whatever that is at the start of the video!) you might want to add a note that comments made below the video may not be read and to become a member of your forum go to (this address!)
That way if someone posts a question below the video and you happen to miss it they can't complain that you are ignoring them.
I do wish youtube would give the video posters more power over their own channel, but I guess they are only out for money and know that there is nowhere else that you can go and get the same exposure.
Good luck and hope you manage to keep the trolls at bay here!