Welcome to Flyer Talk JesseKHall

If you want to use a OW RTW fare you'll need to modify quite a bit to meet the rules. Some flights are codeshares which are invalid for the fares.

A perhaps bigger problem will be getting availability to JNB around the time of the World Cup. The OW RTW fares book into a fairly cheap booking class which means there may well be zero available near world cup dates.

For what it is worth, other than ANC the trip could be done on Star Alliance RTW although would need adjusting to meet their rules (eg max 39k miles).