Thanks for the advice. Ticketing changes have been worked out with AA at no charge as per the rules. The revised itinerary is:

JNB-HKG-DPS-HKG-NRT-MIA-GCM-JFK-YVR-DFW-ANC-DFW-LHR-TLV-BCN-HEL-LHR-CPT-JNB,

which will no doubt be subject to additional changes later on in the trip!