I had some schedule changes that amounted to me being bumped on the next flight after a connection in ORD. They staunchly would not bend the minimum connection time by two minutes (even though both flights in ORD were mainline, thus both gates in the H/K concourse). With DFW you can never presume to be so lucky - they could be anywhere.

The plat desk DID eventually let me switch to the first flight SJC-ORD instead of SFO-ORD because it was obvious that I had intended to book the first flight of the day to get there EARLY. Had I not switched to another airport, though, I'm pretty sure I'd have had to stick with it.

Can you get confirmed on the NEXT flight out of DFW, then get put on the standby list for the flight you actually want?