Okay, so today I got an agent on the phone and just told her I wanted to stop my flight in DFW from SYD. To please remove the USAir portion DFW-CLT-MIA. At first she said, well just leave it and don't board. I said, look I'm trying to do the right thing and not take up a first class award, besides I will be booking another flight and don't want to risk being doubled booked.
So she checked with someone, fearing I would get charged some fee, but came back and they removed those segments at no cost (which I already knew). I've already got an updated ticket.
Then I went into my on hold DFW-MIA and "purchased" the two DFW-MIA U bookings at 25k a piece. Its says U, not Z. I know there isn't a business section on that aircraft, but they'll figure it out, I have my seats 3 H & J.
Yeah, I shouldn't have had to part with another 25K for my portion, but this is a trip of a lifetime. The only thing better will be if another SYD-DFW U seat shows up for my daughter. The worse scenario is that flight back from SYD is delayed and we can't make the 6 pm. direct flight to MIA. Right now we have a 4 hours layover, so I'm thinking positively.
I appreciate all the support and advice here. Thanks