I would go and ask how they achieve the certificates and why others have homework etc. and your ds doesn't. But I'd go and speak directly to the teacher and want a response now. I know if someone asks me a question, however important, if I don't write it down, or answer straight away then they may never get an answer, so she's probably forgotten.
I would go back to the teacher before approaching the head, as most of the questions won't necessarily be answerable by the head without speaking to the teacher first, and you haven't approached the teacher (as far as I can tell) over these issues. You may find the teacher easier to approach if you say "I'd like a quick word about a couple of things, when is it best to talk to you."
I don't think that you can upset a teacher by saying your ds would love to get a certificate, how can he get one? You can also go the same vein and ask how they're supporting the children with parents in the military, "as, you're sure the teacher's aware, that ds's dad is away." My ds (also year 1) wouldn't have told me that sort of thing, I only know he's doing SALT at school because the school told me-he's said nothing, and he has daily sessions!
The reading book and writing homework is something that I've seen happening at school, and isn't about trying to leave behind the "younger and less bright ones".
I spoke to someone in dd2's class (in year 2) who was put out that her dc wasn't getting a new book more often then twice a week, and her dc had told her some children got new ones every day. Every day the teacher stood at the door, and said "If you've read your reading book, please put it in the box to be changed". So her dc only got the book changed twice a week because they were her reading days, and the other days she chose not to have it changed.
Once she'd spoken to the teacher, the teacher took to asking her dc specially on the way into school, and it was changed as often as they'd read it.
They also get writing homework when they get to a certain level of reading. It's very much an optional homework, but they have a special book called "Reading investigation" or something like that, and a set of exercises that they can choose one or more to do on a reading book. It's along the lines of "Find three "wow" words in your book and write a sentence using them." Or "Draw a character from the book and write some words describing them". It's not that they're rewarding the brighter ones with homework (!) more that they feel that the ones who find reading more difficult are concentrating on reading the book, and those who are further on in reading they want to look deeper in the book, rather than just rush through reading, without worrying about understanding.