You note this at the end, but just to reinforce: looking at the maximum range of the aircraft is pointless here, because airliners don't fly with full fuel unless they need to. Surplus fuel means surplus weight means you burn more fuel than you need to. They fly with what they need to get to the destination plus a margin, so a pad on top of the KL->Beijing distance is the right number to look at.
And even then it assumes that the aircraft was at or near FL350 for the duration of the flight. If its altitude didn't remain constant (or its speed), fuel consumption is going to be affected by denser air at lower altitudes. So going off the figures of KL -> Beijing, plus reserves, is the best bet for the absolute maximum range of the aircraft in question with actual travel distance potentially being less. Examining the rules for fuel reserves might be a good place to start, as illustrated in this conversation [1].
As you pointed out in one of your other comment, the way MH370 was so badly mishandled will probably dramatically affect the outcome of our ability to ever find the aircraft. Although this data is interesting, I'm not optimistic there's anything much we can do with it that hasn't already been done. I suppose it serves as public evidence that the aircraft was indeed flying for the claimed duration earlier news reports suggested. But I don't recall anyone who was in disagreement with that figure.
Conspiracists are undoubtedly quite happy to see this data, and although it's fun to consider outlandish possibilities, I wouldn't dare try my hand at speculating what the "ufologists" must believe happened.
