I am considering booking an LONE5 with the following itinerary. I've run it through the Oneworld Itinerary Planner, and I think it comes up fine, but I wanted to get opinions here. I figured the experts on this forum would know of any possible pitfalls.

JFK-EZE//UIO-SCL-IPC-SCL-LIM-xLAX-xHKG-TPE-HKG//JNB-LVI-JNB-CPT-LHR-EWR

I also have the following questions. I've searched here and gotten some guidance, but I haven't found these specific answers:

1) If I am traveling on a LONE5, does Oneworld put any restrictions on purchasing a separate ticket for and traveling on an additional flight on a Oneworld carrier, when that additional flight would not fit into the rules of the RTW ticket?

2) If I leave any segments open-dated, how long before I want to fly would it be advisable to set the flight date for that flight?

3) There are mentions of taxes and fees throughout the board. How can I get an estimate of what those taxes and fees would be on this itinerary?

4) Do you advise I book through the AA RTW desk as opposed to online? I realize that the AA RTW desk can leave segments open dated, while the online system cannot, but is there another advantage?

Thanks in advance for any advice,
Eliza