I'm attempting to book an LONE5 and have a couple questions regarding my prospective route for a worldwide backpacking trip, which is as follows:

LHR-AMM-BCN-SCL-UIO-LIM-GRU-EZE-SYD-BKK-DEL-NRT-DPS-HKG-JNB//EBB-LHR

(1) I'm based in the US but starting my itinerary in the UK to take advantage of the significantly cheaper fare for tickets originating there (I'm a poor recent college graduate). It is my understanding that booking online allows you to pay the fare based on place of origin with no difficulties regardless of where the paying credit card is from. I have also made sure to book with the first segment as one that tickets through AA (RJ flight to AMM) to avoid BA's higher fuel surcharges. Is this the only possible way to book my flight from within the US and take advantage of the lower UK ticket price?

(2) It seems the most difficult segment to book is going to be the one which takes me from South America through SWP to Asia. Using the online booking tool I had a valid flight from BUE-SYD a couple days ago for mid-March, but it has since disappeared. Same with an earlier practice itinerary in which I had a SCL-AKL flight booked that later disappeared. I am extremely flexible with my dates and itinerary, and am wondering if there is ANY reliable flight I should be able to find and book between South America and SWP (I'll be making that flight in mid-to-late March)? If not, I imagine I'll have to give in and get to Asia via North America instead...

(3) Although apparently the NRT-DPS direct flight exists, I cannot find any dates with availability. Is this flight simply impossible to book on an LONE* ticket? I would like to make it to DPS but can interchange it with another destination if necessary. Any recommendations?

Any other comments or suggestions would be greatly appreciated. I am extremely flexible in my planning at this point, on both dates and destinations. I'm starting my trip in early January and hope to travel until late August, at which point I'll be returning to the US for grad school.

Thanks in advance for the help, I've been lurking for a while now and this forum has been invaluable in figuring out how to book my trip.