The catch is that your math is incorrect. Bonus miles do not count towards the q-point calculation. Also, some fares only give 50% q-points.

Essentially, the rule of thumb is that first, business, world traveler plus get 1.5 q-point per mile flown. Economy depends on your fare class and the airline. L on AA gets one point per mile flown, but can be less on the other airlines.

So SYD-SIN-SYD would get 11721 q-points (7814 x 1.5). Your itinerary as it stands would get you 37306 q-points because IB and AY only give 50% for L fares. Actual miles received will be even lower. Then your flight to LAX would get you 14976 q-points, assuming you bought it in an appropriate fare class.

That brings your total to 64003. You still have a ways to go for exec plat.