The answer lies in point 3 "CHARGE APPLIES PER PRICING UNIT".
Your intended itinerary only contains one pricing unit, the open jaw return to ALA/TSE, which means that the cancellation fee will apply only once for the whole ticket provided you cancel before travelling the first segment.
After departure of the first segment, cancellation of any segment will require repricing according to the new itinerary flown. As the fare you have chosen is a deeply discounted economy fare, such a cancellation will inevitably result in forfeit of the entire fare.
Thanks. I never knew what pricing unit means, but you have just enlightened me. Although this is a three part flight, SIN-ICN, ICN-ALA, TSE-SIN, the fare rules seem to clump SIN-ICN-ALA as one. In any case, what you said about pricing unit still stands. Perfect. Penalty is capped at $150. I will keep in mind the caution about after-departure cancellations (likely won't happen).