Counting the window rows seems the only way to establish the size of this vessel. All other scaling features are arbitrary, really: we have no idea whether the lifepods would be designed to hold one man or thirty, or whether the bridge is supposed to accommodate two dozen officers or just two people.
The window row count does support the idea that the ship would only be about 170 meters long, that is, Defiant-sized. She's admittedly taller, but the broad forward hull doesn't extend all the way to the stern, reducing habitable volume somewhat. There could still be room for hundreds in there, but it's not implausible that all the machinery would take up enough room to squeeze out everybody but forty.
Although I think something like 80-120 is the more realistic crew size, with the quoted 40 a special case for the USS da Vinci where extra space is taken by the unique engineering arrangements. I don't think other Saber class ships have featured in novels much, and canon doesn't give us any specs; the DS9 Tech Manual in turn is a hopelessly confused mess as regards the ship specs section at the end, and should be disregarded.
The ship IMO is a corvette of some sort, and the factual successor to the Miranda class, even if said older class is a frigate or somesuch - the same way modern "small" cars are the factual successors of yesterday's "medium" cars. The standards have changed, is all.
Timo Saloniemi