I am following you now on Vimeo.. but really YT Private
should not be that buggy. It is not about having some magic account that may or may NOT work..ANY one with a YT account and an email should be able to view your private video..it is just buggy is all, and always has been, for years actually. I used to use it for clients..but switched to just unlisted. Not sure why YT has never fixed the issue.
If you go to YouTube (Google) help forums this has been an issue since like 2009...if it makes you feel better here is a message from 7/23/2012
Google fumbled on this one. This is soooooo difficult to share private videos, you'd think Microsoft did it! And their official "instructions" on how to do it don't even correspond to what I see on my TouTube screen. Very frustrating!!!