so I went with production order and just accepted that stardates were only roughly sequential. YMMV.
Indeed. I came to the same conclusion about stardates long ago... but having done so, I gave up on trying impose any rationale on them. You seem to be trying to straddle the fence? (Not a judgment, just an observation!...)
I look for
other shreds of evidence from which to interpolate things. We know from "WNMHGB" that Kirk and Mitchell met at the Academy 15 years earlier... and from S1's "Shore Leave" that Kirk was still a "plebe" (i.e., freshman) 15 years before
that point... so it's reasonable to assume that those episodes are no more than a year apart.
If we're willing to accept 24th-century evidence, we know from "Q2" (VOY) that the FYM ended at some point in 2270, so logically it must have begun sometime in 2265. Taking "WNMHGB" as the earliest TOS episode, then, it makes sense to place it in '65 (either just before or just after the FYM began; it's a matter of interpretation, but I prefer the former), and "Shore Leave" in '66. That means KIrk entered the Academy in 2250.
We know from
TMOST ("quasi-canon") that Kirk entered the Academy at age 17, so that gives us a birth year of 2233. (Making the month and day match Shatner's is pure fanon.) We know that Kirk was 34 in S2's "Deadly Years," placing that one sometime between his 2267 birthday and his 2268 birthday. We know from "Private Little War" later in S2 that Kirk's "first planetary survey mission" was 13 years earlier, so if we make the reasonable inference that said mission came just after his graduation following four years in the Academy, that would be 2254, putting the episode in 2267. That limits the earlier "Deadly Years" to that year too, as well as "Journey to Babel" (marking 18 years since Sarek last spoke to Spock, hence 2249), and presumably most of the rest of S2.
And so it goes, with further interpolations. If S2 mostly occupies 2267, then S1 (the longest season) mostly occupies 2265-'66, putting "Errand of Mercy" in the latter year, which means S3's "Day of the Dove," set "three years" after that episode's peace treaty, falls sometime in 2269. I wind up with room in the back half of '69 for TAS (which
really plays havoc with stardates), and 2270 left over for tales never shown on screen (e.g., lots of novels... although a few of them do fit in among earlier episodes, it's not as many as one might expect).
That's the quick-and-dirty version of the logic behind my take. (I have all the details in a spreadsheet.) As you say, YMMV.

FWIW, though, I do
agree with you about the dating of the movies... specifically, putting
STII and
STIII in 2283 (even though it still requires a
little fudging of the span since "Space Seed"), and
ST VI in 2292 (in contrast to the more typical '85 and '93 dates).
There is no mention of The Organian Peace Treaty in Day of The Dove, Kang is probably referencing it I agree but it's not mentioned as such while the only time we do get to hear of it apart from Errand of Mercy is in The Trouble With Tribbles where koloth quotes it to Kirk on Space station K-7!
Okay, technically that's correct. Kang's exact words were
"For three years, the Federation and the Klingon Empire have been at peace. A treaty we have honored to the letter." Given the earlier reference in "TWT," though, and the fact that we've never heard of any
other treaty, it does seem reasonable to infer that they're referring to the same one.