What's the rest of the galaxy? Either the Romulan Star Empire sits at the edge of the galaxy or at its center.
Or then it consists of the planets Romulus and Remus, just like the dialogue says, and that's it. Hence the extremely curved RNZ that encompasses this minuscule volume of space and separates it from the rest of the universe.
The speed at which messages travel is dependent on more than distance: Sigma Iotia was not within realtime communications back when the Horizon
visited them, but was when the Enterprise
did. What changed? Somebody probably installed a few communications relays!
I don't see how this can be interpreted in any other way than explicitly stated by chief engineer Scott.
Who is a fallible character with zero right to draw conclusions on a vessel he can't even properly see!
Naturally, in the original destroyer vs. sub story, the destroyer crew would have the specs of the sub down pat - their side operated subs of their own, after all. But that part was poorly carried over to the scifi story where no such knowledge should be allowed.
Why do you follow this with an argument that this particular ship cannot have been FTL, though? I already pointed out that that part is completely irrelevant to whether the Romulan culture knows how to travel at warp.
Except, of course, this particular ship does
travel at warp on several occasions - say, when its course is guesstimated on a chart where the emergency warp speed of the hero ship was previously observed and the "speed scale" thus established.
And no, I'm not speaking of the Enterprise
approaching the map area from the left - three-dimensionality might affect that all right. I'm talking about both the Romulans and the heroes moving from outpost to outpost - an inescapable benchmark for their more or less equal speed.
You are arriving at your conclusion based entirely on a two-dimensional map (apparently a simplified graphic for the ship's crew to apprehend the situation) which lacks three-dimensionality.
Umm, what conclusion? That Romulans have warp drive? No, I'm just saying that there is no episode of TOS that would ever claim that Romulans did not have warp drive. Any reading of such a thing in "Balance of Terror" is a misreading.