Your tour takes over 3 minutes to show the first scene over my connection.
I would expect the skin and all elements to load along with the first scene before anything else. Other scenes should only start loading in the background after this.
Adding video adds another complication into the mix, as I'm not sure what or where the loading procedure is for these. I would have thought these would be a totally separate stream and independent to the tour itself.
The question are: How large is the first scene in megabytes? What is the starting/first panorama image in pixel size? Is there audio on the first scene? You appear not to be making use of the two stage display options for normal and fullscreen viewing. Doing so would reduce the time to initial display considerably.
It is hard to pass comment without having the project files and testing them. I suggest you build some testers and see where things slow down after adding components and scenes.