Yeah, I can't cope with too many statistics. I leave that to others on the forum!
As for age standardisation, it is what it is. Can't change the fact that older children will lose a few points and younger ones will gain a few points, relatively speaking. It is done in the interests of fairness so just have to roll with it.
All my DCs are young for their respective years. My youngest is very young for the year and the difference between him and those who were September babies is very apparent, especially at this age. I don't consider him to have any "advantage" through age standardisation as he struggles in so many ways. Ideally we want to try and get our DCs several points over the minimum so that age standardisation doesn't affect their places, its borderline candidates for whom those extra few points either way make the difference.
I think getting too deep into the age standardisation is unhelpful, if just opens the way to more "what ifs...?", a form of mental torture! Celebrate how well your DC did rather than worry about it. It really is only a matter of a few points