Just noticed something when you did the seal installation close to the end of the video. It might help to put some RTV up , into the rear part of the cavity of the tailshaft where the seal butts up against.
Alot of times there is a little bit of fluid that weeps from this area. It's the same thing that is done when replacing a pinion seal. RTV sealant should be applied to that back area that the pinion seal butts up against.
Many times we always are fighting to solve these leaks even when new seals are put in . This method solves that pesky leak issue.