I would request stopovers for all of the plane changes in MIA. In the US, there is little difference in taxes/fees between stopovers and transits. Call the AA RTW desk in the USA, and have them create the PNR with open segments after HKG-YYZ flight. Also tell the RTW desk that you live in Canada and will purchase the ticket at an AA airport location. When ready to actually buy the ticket, call a day in advance and make sure that they have properly set up the ticketing. Go to the airport, and buy the ticket. Since it will have open segments, you will receive a paper ticket that should just print-out from the machine. I would suggest going during the week and during the 7-4 daytime shift so that the staff can call the RTW desk if there are any snafus. It should be fairly easy to do overall.