Welcome to EvC Immoros. Not a bad first post, not bad at all.
I think that you're even right as far as you go.
However, the use of the word circle instead of sphere isn't the only place where we can learn what the writers were thinking. There are other places in the bible. These others make it pretty clear that the authors did not think the earth was a sphere.
They'll come up pretty soon I'm sure. Perhaps you'd like to discuss them before others do?