Thanks for all the help guys. So at the moment, my plan looks a little like this.

FRA-xDFW-SFO-LAS-LAX-YYZ-ORD-JFK-SYD-NRT-BKK-HKG-SIN-LHR-DXB-xLHR-FRA (then purchase a one-way back to LHR)

I do have a few problems though. It lets me fly DXB-FRA via LHR no problem, (in effect violating both the 2 stopovers in Origin rule and also the flying return between the same city pair rule), but it counts DFW-SFO as 1st of the 6 NA segments?

Reason I ask is I am trying to book one more segment into NA. I know I can buy extra segments at 200GBP but am just trying to get clarification here. Perhaps there is an email address for RTW Desk at AA? I assume if I do add a segment I have to email them to get a quote.

Also, peaking of the AA RTW desk, the lady who answered last time told me I could not book an open-ended ticket even though theres a section in the rules that state (for travel starting in TC2/3): "Reservations for the first international flight and all preceding flights must be made prior to departure. Subsequent segments may be open-dated". Was she just wrong and I should have argued it with her?