Time to rethink your itinerary. Flexibility and contingency options are the key because reward seat availability is not consistently reliable. If you have stretched your mileage so thin that you have virtually no routing flexibility left then it's time to re-examine your priorities and expectations. Don't be greedy.
I find it helps if I can visualise our intended route easily by plotting it on a world map. If you are stretching the mileage limit, it's surprising how a map can help you see "wasteful" routings. If your route zig zags too much then it is chewing up mileage. I have found that setting a route which connects stopovers in a circular direction rather than connecting places with crossing multiple times through individual cities (LHR being the most obvious), can save quite a bit in mileage.
Don't discount the benefits of paying cash for some flights to free up mileage on your reward itinerary, especially in Europe. Even though we always book J OW rewards, we often pay for cheap Y flights of 1 - 2 hrs duration to free up miles and allow us to merge 2 or more stopovers into one.
Look at using more BA flights - even though people can be put off by their high taxes, overall they do have good reward availability.
Travelling from Aus to (or from) Europe via the USA will generally soak up 4,000 or more extra Kms than going via Asia/ Middle East. Even flying LHR - JNB - SYD instead of trying for routes via HKG, DXB or DOH can be several 1000 kms less than trying to travel via SFO, DFW or LAX.