Your just playing with semantics here, the old English word 'firmament' is a translation of a Hebrew word that just means, 'the visible arch of the sky'. A flat earth and thinking with your kidneys, which by the way the ancient Hebrews and Greeks thought is was the heart, is irrelevant to the actual message. To the ancients the sky looked like a dome, and they thought of it in that way. It did look kind of flat but ancient Greeks know the world was round, a famous librarian at Alexandria actually calculated the circumference and was only off by a couple of hundred miles. Master mariners generally knew the earth was round, the ancient Hebrews had little interest in such things since they were a land locked nation.