You have had more luck thank I in extracting detail, I fear. Maths I have only been told that he had to circle lots to get back to but then didn't get to them all. Some other boys said there were quite a few "puzzle" type questions, so seems to have been a bit more creative than it might have been.
The comprehension was chapter 5 of Stig of Dump, first two pages. If the vocab questions are an indication ("what is weather-boarding" in the context of a house) I think it was quite challenging - none of the 4 sitters I have heard reports from finished it.
Having a letter format for the composition was a little unusual - my boy did not find that very inspiring, but I am sure a stronger and more sensible writer would have been fine.
There was also verbal reasoning, which I think also had a vocab component, some of which seemed unusally knowledge-based and generally seems to have been viewed as fairly tough. There was non-verbal too, but I don't know if it was in a seperate paper or rolled up with the verbal (shape sequences etc).
If your DS found it not too difficult, I think he is pretty much a cert, as I don't think it is a universal view, even from strong candidates. Good luck - I won't be seeing you next week!