If you start in CAI on your latest itinerary your trip would look like CAI-BCN-MAD-SCL-PUQ-MPN-SCL-PPT-AKL-SYD-JNB-MAD-BCN-CAI and you would buy a separate ticket AKL-TBU-AKL on NZ or WR.

Unfortunately, the above route comes in 845 miles over the 34,000 mile limit, primarily due to the difficulty in getting from JNB to CAI. I've fiddled with the routing as much as I can but don't see a way to shave off the extra miles. You may have to revert to starting in LHR and routing LHR-MAD-SCL-PUQ-MPN-SCL-PPT-AKL-SYD-JNB-LHR.