Are there any documented example usages of film (ie, film film, not video or digital) for in-flight entertainment?
I know film projectors were definitely used on early 747s - converting part of the passenger area into a theater is part of the design. I was able to dig up the photo below showing the projector mechanism, which is pretty impressive to look at.



I'm not sure whose system that is, but it looks like a 35mm projector so it probably predates the TRANSCOM cassettes.

Can't help you with #2 or #3 though.