Not sure about the relationship between the dragons and dragonzilla. After all, it did eat one of the smaller ones that didn't bring it a suitable offering - so not likely a queen-bee sort of dragon. More like an angry and vengeful god of a dragon.

The 'queen' thing was just a suggestion of one of the vikings.

Do you really think the dragons would put up with the humans shit if they didn't like living there? And as Boing said, they never did confirm exactly what the giganto-dragon actually does, besides eat those who displease it.

I dunno. It's unclear exactly what level of intelligence the dragons have, and here in the real world humans are pretty good at bribing/tricking/forcing animals to put up with all kinds of shit.