I basically agree with your findings, Hotdogs, except:
FACT: JWs have always taught that "day" seven can be used to infer the length of the other days. This has been explicitly stated as recent as 1998 (see Creator Book, quoted above). Nothing has been published that contradicts or revises this teaching.
Although the Creator book is obviously more recent than Insight, leaving_quietly's Insight quote shows that the Society has considered the possibility that the other days were not 7,000 years. Notice the phrase at the end "at least thousands of years in length", which is allowing for a range of possible lengths for those days.
That being said, I think that it's probably an unpleasant thought for the higher-ups to contemplate the other six days being different lengths because it intrudes on the circular reasoning behind day 7 being 7,000 years. If the other days were longer then it brings into question why this one has to be 7,000 years and not longer. So most WT quotes do seem to be hinting that they want all days to be even in length, but they're still avoiding any definite statements about that.
For that reason I still urge caution in making an assertion about something which does not have direct quotes from the Society to back it up. I know it's tempting to say that they believe this since it places them into a clear conflict with science, but even in the Creator book they are only saying "the other days must be thousands of years long", without using any wording like "of equal length to day 7". We may think we know what they are getting at, but it's not spelled out, so it's easily deniable on their part.
FACT: If the "end" comes as soon as JWs say it will, "day" seven will end up being about 7000 years long.
FACT: All six creative days are described as encompasing "thousands" of years each. The only reason for this slightly vague choice of words is that JWs cannot pinpoint the date of the beginning of “day” seven (something they once tried to do: 1975 fiasco) and therefore cannot know exactly how long it will end up being.
No, day 7 is still exactly 7,000 years, in their opinion. It's just a question of when the day starts. Clearly Franz' date of 4026 B.C. was wrong; even if it were the date of Adam's creation, it seems that Eve's creation was more than 39 years later or else the 6,000 years would have been up by now and Armageddon would have come. This simply means that Eve's creation, the final act of day 6, happened after the fall of 3987 B.C. (if my math is right). It doesn't change the length of day 7 in the minds of the WT leadership.