Well you don't believe the Christian presupposition that the Bible's authors were inspired to write what they did. That's why it's called the Word of God. Thus, I'm not sure the conversation can do any good by continuing.
Also in those verses it says the Earth cannot BE moved not that it isn't moving. What I get from that is basically God helping us understand we humans aren't nearly as strong or powerful as we like to think we are. Similar to what he said to Job.
Was going to say something similar to this, but it sums it up nicely.
The claim seems to have an underlying assumption that it is impossible to be "fixed" and "immovable" and yet orbit around the sun. But the fact is, the earth has proven itself to be fixed and immovable:
• The earth is fixed and immovable in relation to its orbit around the sun. Have you ever known the earth to "unfix" itself and "move" itself out of its orbit around the sun? It doesn't happen, because the earth is fixed and immovable in relation to its orbit around the sun.
• The earth also is fixed and immovable in relation to us. There has never been a single day in which we had no place to stand, because the earth unfixed itself and moved itself out from under our feet.
The earth has always been fixed and immovable, both in relation to us and in relation to its orbit around the sun. In fact we've learned to take it for granted that the sun will shine during the day and that there will ground for us to stand on when we awake in the morning.
Having said that, one should at least consider the possibility that the verses cited above are actually using a figure of speech, to express the permanence of God's will and the permanence of his creation.