First, sorry to the OP for his debacle, and glad he was able to salvage at least most of his vacation.

Second, I am curious how long SQ has been allowing partners to redeem C/J awards on their 77W long-haul configuration and whether others in AP have had success redeeming their miles on the SFO-HKG route in C. In the past year I've read posts of some folks finding C awards on SYD-SIN using *A points, and there were reports of a few awards on JFK-FRA on the A380, but this is the first I've heard of C awards being made available (at least in theory although not in practice due to the shameful treatment of the OP) to *A partners' FF programs on this route in maybe 6 or 7 years. I almost wonder if the SQ agents refused to allow the passenger to board because of something related to SQ's long-standing policy of not allowing *A members to redeem for C awards.