You’ve pretty much got it as far as I know. Although I think the mono mix was on some 35mm prints, not just 16mm, and was also released in 1977, shortly after the film premiered on 70mm, to theaters that weren’t set up for stereo or surround. I believe the mono mix was also used for airings of the film on TV/HBO. And yes, the 1985 home video version was identical visually to the 1981 prints (and was also released as a widescreen laserdisc and later VHS, so not just pan & scan), and the audio was almost identical to the 1977 stereo mix with the exception of the 3PO line that was added in from the mono mix. I’m not sure about those different composites and credits you’re talking about, never heard about that. Someone else will have to chime in.

And yes there were a few 8mm home releases, but they were not the complete film. Just selected scenes.

As for sources for the pre-1985 versions, well it’s mostly film reels. The 1981 version was released on a few VHS tapes and laserdiscs (I think all fullscreen) with the original audio during the brief period after its release but before the new mix was put out in 1985. And since the 1985 and 1993 releases were the same except for the audio, this was the version seen on all home releases until the SE. But Star Wars exactly as it existed in 1977, with both the original crawl and audio mix, has never been seen on home video in any form or quality, sadly enough. The GOUT DVD that had the original crawl had the 1993 mix and the early VHS/LD releases with the 77 mix still had the ANH crawl.

So that just leaves film reels as the only pure sources for the original theatrical version. If you want to see it today, though, you can of course get the SSE (most authentic) or Despecialized (best quality) if you haven’t already. That’s clearly your best bet, sure beats hunting down old laserdidscs and VHS tapes, but you probably know that if you’re on this site.