Just my 2 cents.
In one of the books, I do not remember which one, it talks about making deckplans and says that only about half of the quarter allowence for staterooms are used for the staterooms themselves. The rest is used for passage ways, lounges, mess halls, med bay, etc. Being ex-Military, I also know how duty shifts work. Gallery work would be a temp duty. Example. I was a Avation Hydralic Tech but several times during my service, I was tempory re-asign to "Other" duties. These temp assignments would last from 1 to 6 months depending on the job. Although I was never assign to the gallery, it was a possibility. The Galley would most likely have 1 or 2 personal on a small ship pemently assign to the job with additional crew needed being supply by temp personal assiting them. Larger ships would have more "perment" crew, but would still fill out the need manpower with temp crew. (You do not need to know how to cook to serve in a food line.) Also, to help make things manageable, the meals could be serve in shifts. This would allow the Mess hall itself to be smaller since it would not have to be able to serve everyone at once. This was how it was done at Boot Camp. Each unit at a asigned time for each of their meals. Also, bulk frozen foods actually take up less space then pre-pack meals. Finally. Has a it has been said, the galley can serve additional functions. It can also be used a lounge, a classroom, a debriefing room, a rec room.