The pods look like they have more volume than an Oberth in its entirety. Perhaps even a Nova-class. But do we know their dimensions?
We'll chalk the torpedo tube scene up to VFX blunders, then. Canon purists can argue differently, but I don't see space for one.
What is wrong with the Saber scaling? How big is it supposed to be?
I thought I had read a blurb in the TNG Tech Manual regarding the internal volume of the Galaxy primary hull was something like 35% free space? If so, there should still be plenty of room for extras even in the Nebula, I would think. Earlier, less gee-whiz components than the Galaxy, yes; inferior components, no. And being the next newest design down from the then state-of-the-art Galaxy, I would think Starfleet would work diligently at correcting any such flaws, especially if they're the workhorses of the fleet.
Do we know from episodes or Trek lit if the Nebula has saucer separation capability? I am inclined to think it doesn't...rather, certainly it has an emergency separation function, but I don't think it has an easy disconnect/reconnect like the Galaxy does.