16mm at drive-ins? No way. They would have been 35mm, just like any other regular cinema.

I have no idea if those 35mm prints were of the early cut, or if all 35mm prints were of the more familiar version. Didn't 70mm prints have a longer lead time due to the extra work? (The first Star Wars would have been an exception; I've heard Ben Burtt talk about how the Dolby Stereo mix had to be rushed out so that it could be tested for the wide rollout of the system, so I'm guessing that the 35mm prints were made first in that case.)

I'm not sure how we'd be able to conclusively figure it out. On TrekBBS, I once asked a similar question, if any early 35mm prints of Star Trek II just said "Star Trek: The Wrath of Khan" like the 70mm prints did; I never got an answer on that.

As for that frame, I think it's 70mm. My guess would be that the later prints made in summer '80 were of the revised version. There's no reason why this second wave couldn't have been derived from the "fixed" version.