The number at the end of the film doesn't indicate the amount of stations on the island, but the amount of films produced for this patricular station. This is likely, because it was already confirmed that there are Orientation Films for every station and there were already discovered more stations than six. The number at the end might indicate either a different edition of the Orienation Film (maybe for other instructions for the station's staff) or differnet parts for one station (but unlikely because an introduction would not take place in a part 3 of 6). Furthermore, the DHARMA Initiative was already on the Island before 1980, confirmed by Ben's Flashbacks and other sources. Therefore, producing videos for already existing stations would be not logical.
I like this theory because it would explain something that's been bugging me for a while now. We know that Pierre Chang had made Orientation films for at least 3 stations before the Swan - Hydra, Arrow and Orchid - because Chang does not have a prosthetic arm in any of these, and The Incident, which caused him to lose his arm, happened before the Swan film was made. That means that the 3 of 6 cannot mean that it was the third film made. And if a new series of 6 Orientation films were made at a later date, and the Swan was the third of them, then the other stations would almost certainly have films from this series, but they don't. The only explanation is that there were 6 separate films made just for the Swan.
The Swan orientation is on film, and Pearl one on tape because film is a medium impervious to the Swan's electromagnetic fields.
The fact that the orientation film exists suggests that individuals stationed in the Swan were simply part of an experiment, and had no prior knowledge of the true goals of the DHARMA Initiative and the Hanso Foundation. However, it could be that the project is a well-kept secret and that participants only learn more about after being stationed on the Island.
Sensory deprivation was employed in parapsychology experiments during the 70's and 80's, especially with those involving clairvoyance and telepathy. Supposedly, if the subject's brain was not receiving input from the normal five senses, he or she could then tune into the psychic senses. The man in the contraption in the film may be in such a sensory deprivation test. Since the footage appears when the word, "Parapsychology" is spoken, this is quite likely.
Radzinsky edited the film because he wanted his replacements to stop pushing the button, thereby triggering a system failure that would give away the location of the Island.
He removed all information about the nature of the Incident and the consequences of a system failure because he wanted the viewer to suspect that nothing will happen if the button isn't pushed.
He left the reference to B.F. Skinner in the film because he wanted the viewer to conclude that the Swan Station is nothing but a giant Skinner box.
He removed "Dr. Candle's" warning about contacting the outside world because he wanted the viewer to attempt such a contact. Perhaps this implies that the outside world can, in fact, be contacted via the DHARMA computer system, or at least other stations, In fact, is not a good idea to have the Pearl contacting other stations, so they could realize that they are the psicological experiment and this could lead to the incident so they warned it in the new Orientation video (assuming the video we have seen is a new version of the Swan Orientation).
He smuggled the deleted footage out in the hollowed-out Bible for the same reason that he and Kelvin hid the map on the blast door -- because he knew that someone was watching him, and he didn't want them to know he was trying to sabotage their work.
The video contains the history of DHARMA as this would be the first station that new recruits are stationed at, (with an experienced partner, like Radzinsky (experienced) and Inman (new)) if they could handle the button pushing for the 540 days, they were suitable for different DHARMA stations \ experiments.