The most expensive domestic flight in US that has change fees would be what - $600?
So the OP cancels a ticket worth $2k instead of paying a change fee on the other PNR or sucking up the fare loss
what about prepaid accom/transport/events etc others in this situation may have paid for already?
I'm sorry I've re-read this thread and I'm confused as to where the $2k value comes from - they were talking about a FF award ticket and I'm not sure any real valuation can be put to it(I suppose the cheapest fare available at time of booking may qualify, though I'm still a bit iffy about that). Did I miss something obvious? (probably

)
Anyway US fares are not really relevant to the point in my view - kind of apples and oranges. You wouldn't compare a SYD-PER fare (revenue or award) with a SYD-BNE would you?
Now the OP didn't say (that I saw) if the fare purchased was flex or not or a YUPP or not so it's hard to know.
I do understand the point you're making, that perhaps the OP should NOT have cancelled the award(which are hard to find) and worked on solving the shorter sector within the USA to make that work - I'd tend to agree with that
I do feel the OP's contention that QF had no sympathy or perhaps they should have allowed the change at the same "price" (though if an award seat was still available on a flight to make the connection work, then it would have been a change fee in points wouldn't it? and thus the "FF sale points amount" wouldn't really apply to my way of thinking). At any rate, to me, QF were acting appropriately to the situation - a request to change an award ticket to a different flight which would accrue fees or charges appropriate at the time of the request.
Given award seats on QF almost barely exist (as a % of points to members) - the OP was never going to find an award seat replacement and most definitely not at the same discounted rate. Through no fault of their own the circumstances are changed by the operating carrier and yet the carrier holds zero responsibility? While according to the rules and policies this may be the case - the simple truth is that the OP feels let down and has lost faith in QF on an aspirational award redemption. This - my friend is highly damaging for loyalty.
Oh, I agree totally but in the event of schedule change by the airline they are required to offer a reasonable alternative that the customer is happy with, or the customer accepts the change, or gets a full refund (OP's option). Now we don't know the full circumstances of what the change, or offered alternatives were - are we talking 5 hours difference? 12? 24? if your original arrival is on say QF93 at 0630 and you're moved to one of those later flights out of SYD to arrive at 1400ish (I am taking times from memory here) then QF should attempt to offer something to arrives within a couple of hours of the original schedule.
QF holds "zero responsibility" for ensuring a connection to a flight that is not part of that booking. Now yes, you'd hope if you explained to an agent that "I really want to keep that 06030 arrival as I have a flight booked to Chicago at 10a that I'd miss if I was moved to arrive after 1400"(for example) but QF is under zero obligation to honour that request or go out of their way on that, because that flight is not part of the affected booking.
I absolutely feel empathy for the OP for the situation, but these are the risks we face for booking separately. Yes, it damages their brand in the eyes of an affected person like this, but also the buyer should take responsibility for their own choices in booking separately (and I'm not saying the OP hasn't done this-I think from reading that they understood the risks and it seemed the only alternative was to cancel the award).
My question now for the OP is - did you cancel that other booking? Did you find another way to the US to meet up with that flight? or make a totally new booking to the final destination? (or just nuke that trip ?)