Well, I presume you will need many of those documents when you work with the Aussie embassy, correct? So it might be good to have them readily available. Again, no need to volunteer them up front but have things in mind you can readily pull out if it gets to that point. I don't think you can ever have too much information. The prep work is good but don't let it get you too stressed out.

You have a legal visa and a legal reason for coming and the border agent is trying to sort all that out. Granted some do that in more friendly manner than others.

There are some US border agents on this board who might also chime in with more practical advice.

If you miss the flight then yes, you will be staying at a DFW area hotel until the next morning. Who pays for the hotel? I think that normally depends on what caused the delay (weather, or mechanical, etc.)