I just skimmed, so I may have missed one you had.
I would add-
The Enemy Within - the original transporter malfunction, and I think it's a fun episode for Kirk.
Mudd's Women - Not as good as I, Mudd, but I think it's still a good episode thanks to Mudd and the chicks.
The Devil in the Dark - it's cheesy, but it has some iconic moments for Spock and McCoy.
The Gamesters of Triskelion - Not one of TOS's best, but still a classic.
And maybe-
This Side of Paradise - I like Spock's turn here, and Kirk dealing with it.
The Deadly Years - not great or anything, but I think it's a fun premise
Whom Gods Destroy - I really like this one. The characters are a lot of fun, and I like the way it plays out.
The Cloud Minders - A solid take on a scifi standard. And there's that chick who goes after Spock.
Wildcard-
Spock's Brain - It's so bad it's good! It's so notorious for being the worst episode, that I think it's a must. It's stupidly fun.
And I would take out-
Tomorrow is Yesterday - I guess I could go either way on this one. The City on the Edge of Forever is the only time travel episodes I consider necessary for TOS. It has a decent theme in there with the guy they pick up, but overall I don't think it's a great episode. Meh, what the hell, looking over some of the episodes I'm suggesting, keep it.
Obsession - A very forgettable episode to me.
I'm surprised that I'd actually mostly
add to your list.