Just watched your video. You might need to test it out more, you really missed a lot. Here is a video by someone else (older version and in german only):
The button (upper left corner) is for re-adjusting to the height of your headset only. The button right from that is for free positioning. For YouTube and Vimeo videos, full screen becomes available when the browser parsed the links. A button appears in the right upper corner, but full screen will only work with videos that allow embedding (this is a restriction that comes from YT and Vimeo and how they cope with this browser engine).
Besides that, sadly the way you streamed the presentation, didn't show the pass-through feature. I guess that's because of the privacy settings.