Once the trip has started the OP is at liberty to finish the trip anywhere he likes (at the risk of forfeiting the remainder of the itinerary) but my understanding is that a 140K, 280K or 420K RTW award itinerary needs to have a return to the city of origin included in the itinerary prior to the trip commencing. After commencement you can cut it short if you want to (obviously QF can't "take back" any part of the trip which has already been completed) but my understanding is that the OP wants to include another stopover somewhere before reaching Bali and terminate the award in Bali so that his stopover there isn't counted. I think that if he tries to do that QF will say "You have to include a return to PER for it to qualify as a OW RTW award - and Bali would therefore be the 5th stopover city, which means you can't have another one".
I guess it depends on how you interpret this rule:
Rule 14.5.3 A one way oneworld Award Itinerary will be charged as a return Itinerary. oneworld Award Itineraries finishing in a port other than the port of origin must include the distance to return directly to the port of origin when calculating the number of Points required to redeem the Flight Award and the maximum distance for the Itinerary.
I agree that it is clear from this rule that on a OW classic award you don't have to have a return to the city of origin, but my understanding is that if you don't then you forego the capped points benefit of the RTW award. The points required to do a "one way" award would be the sum of the points required for each individual flight segment, in which case it could easily cost you a lot more points than the 140K or 280K that a RTW award is capped at - in which case you're not booking a OW RTW award at all.