Neither of those things will be used against your DS as an individual. The KS2 SATs are just used as statistical modelling to predict outcomes across the cohort. These have been sued for years by schools, LAs and the gov to predict outcomes (your DS may have been give a target grade, for example, which is generated form this). Don't panic about this affecting him as an individual. Our stats guy used these to tell use how many 9s, 8s, 7s etc. we might expect per subject and we , more or less, fitted our CAGs to this.
It's the rank order that matters. Ofqual did respond as someone e said, tot he articles yesterday, distancing themselves form the idea that pupils were set to get wildly unexpected result.
I do think schools have been predicting too many 9s to students in the last year, thereby creating a situation where lots of students become 'disappointed' with 'only' an 8. For context, my reasonably high achieving comp allocated 7 9s out of 400 students for English. We'll probably see about 5 of them get them, I suspect. 9s should be astonishingly good. For my DS he could feasibly get a 9 in 3 subjects but I think he will only be top of the rank order in one : we know eh may get 0 9s. That's OK. Come back to me if my DS gets 7s or 6s for any of those! That may get a different, less philosophical response!
We just have to be optimistic in the face of anxiety!