As i said from the very start you can fudge the numbers by giving the A350 an unrealistic empty weight. The lighter you make the A350's empty weight the more payload it appears to take.
Well, we can say that roughly OEW = MZFW - maximum structural payload (MSP)
Right from A350's ACAP, and using the base model WV000 with MZFW of 192,000 kg and MSP of 53,300 kg, we get an OEW of 138,700
kg for the A359. But that is only for the WV000 base model, since Airbus only issues the payload chart for that model only, it is the only model that has its payload chart published.
Later frames got lighter OEW, A.net members who work for various airlines have confirmed an OEW of 135t-136t right from the manual.
Your 142t OEW is a bit high and unrealistic, and in our case, it would make a huge difference in the payload for the trips we are comparing. Again, SQ22 carried 4.5t more in payload while flying a route that is 5% longer. Had the 789 flew in such conditions, its fuel burn numbers would have been completely different (of course, that's a big if since it won't be able to take off in that condition in the first place, it might weigh as much as 260t in that case)