JT2 - I think you did a great job, by quick thinking, you & your buddy were able to divide & conquer the situation, resulting in everyone going home at the end of the day.
As for the instructor, my biggest problem was in him not telling the same story to the responding EMT's & you/your buddy. Talk about a career limiting move. I agree 80 something dives is far too few to be an instructor. And it was poor judgement to take 3 divers down alone, while teaching his second class. Don't most instructors have a baby-sitter (for wont of a better word) overseeing their first true teaching situations?
Amanda - I have seen quite a few under-trained, overweighted students 'fall' off the platforms. They are cramped, slick with growth, they move as another diver falls on the them coming down and next thing - they are off the platform, heading toward the bottom. If they forget where their inflator hose is - first stop is the bottom. Or they float off a few feet & dump all air to get back down to platform, neglecting the fact they have moved within the water column. It sounds funny, but happens all too easily.
As for administration of O2 or any other life saving techniques, I would have to proceed despite any litiginous reservations. Philadelphia had a couple cases where people were quite literally hit by cars in front of the ER doors. Medical personal REFUSED to treat due to liability issues. Left them lay bleeding on the street. Can't say I blame them, PA jury awards for Med Mal are some of the highest in the country. Since then, PA seriously revised the good sam law. (under PA Consolidated Statues, Title 42, Chapter 83, Section 8331 & 8332. Maybe the lawyerly tpes here can tell me if that is proper citation ) There is no mention of administration or exclusion of O2. It does say that "good faith" shall include, but is not limited to, a reasonable opinion that the immediacy of the situation is such that the rendering of care should not be postponed until the patient is hospitalized. And holds the provider immune from civil penalty. If they got the diver to land, I would suggest the above applies. But again, I'm not a lawyer.
Big T & Mike - I also see unbelievable stuff and that is why I never want to be a DM or Instructor. I'd go crazy! MAybe you guys can sell the video - 'When Good Dives Go Bad 'or something like that.