Thanks very much for posting this!
Here is a link to the video: https://www.youtube.com/watch?v=luultUD0eK0
My understanding is that one EpiPen contains 2 mL of epinephrine solution, and that the auto-injection function dispenses approximately 0.3 mL. So in theory some five extra doses remain post-activation (the video shows four being harvested, which seems about right).
Two comments:
(1) there are side-effects to epinephrine, and overdosing could be dangerous. It would be prudent to obtain medical advice well before the need to use this technique might arise;
(2) the use of the small hacksaw demonstrated in the video (0:48-1:05) looked a bit hazardous: it slipped or skipped, and there was some possibility of an accidental cut to her right hand (especially aboard a moving boat). If possible, the EpiPen should be held securely in a portable vice or similar.

Wilderness Medicine has a youtube video showing how to get an additional two doses of epinephrine by talking the auto-injector apart. This may be very important knowledge when medical care is not readily available.