What brought all this on?
Because the "counting of years" as men do it today (including yours) is unreliable and can be used by others (not you) to decieve and control....did you know the errors of Russell, Rutherford, White, and Camping all grew out of their assurance that they were counting the years correctly? Be careful my brother you have a lot of good sound study in your work but do not be "sure" you are correct in this area...at least note the three reasons for concern I gave...
All the "generations" from sources like the book of the generations of Adam, may not have been brought forward for Moses only those significant for the Lord's purpose (some of his information is from History...the Book of Wars, the Book of Yasher, etc. that being said I of course believe God told Moses what to write in many cases but also led him top these other sources...after all the Holy Spirit saw fit to have him mention them)
The question of the missing or added 600 years between the older source (Hebrew behind the LXX) and the younger conclusions (900 years after Christ) has to make one concerned (if counting the years) which is correct (which do you think).
Then the problem of day/year meanings (especially the problem with creation days 1 through 3 as 24 hours each, 1,000 years each, or possibly more...evening and morning can be transitions from darkness/disorder to light/greater order but phrased for the peoples sake so they could comprehend)....
These three factors (either of which may be accurate) change the timeline going from past to present....
And then
IF the Hebrew counting (although it does not count from Christ) is even near accurate and
IF the return (the parousia) has to or is going to happen
before this Millennium Sabbath (the 1,000 year reign) then that means the man of sin (the wicked one, Anti-Christ) is about to be revealed, and Christ is coming within the next 10 years (which believe me is fine with me) but IF we have already reached the 6th 1,000 years (4000 to Christ and 2000 since) then we are NOW IN THE 7th 1,000 years or Millennial reign...do you see? I am not asking that you agree but that you do understand the logic here! The Lord bless...