Thank y'all for your kind and insightful responses. I've booked the 2-hour connection and have peace of mind with it. SAved a few bucks too.
I am so looking forward to this trip. And I'll be sure to catch the famed MEL Qantas Club on my return...spending the night at the airport hotel so I'll have lots of time to enjoy MEL!
P.S. Yes, DFW/MEL nonstop would be AWESOME!!! Let's go for 15+ hours airborne!