OK – here is my opinion of the ever elusive wheelie –
I don’t think it is a skill that is learned – you either have it or you don’t. That being said, if you do have it, practice is still needed to master the skill.
Watching your video, I think you are not hitting the sweet spot deep enough to control the side torque easily. Try looping out (high enough in the wheelie that you have to step off the back) – after that, wheelie to a point just before that and bring your front end back down by hitting the rear brake. Next – do the same without bringing the front end down, tap the brake while pedaling, to keep from looping, and keep force on the pedals to keep the front end up. If you get to this point you will see that the side to side control is much more manageable.