1. Don't use us. Normally you wouldn't ever refer to yourself in an essay as 'I', and 'us' pretty much has the same effect by referencing yourself. Stick to keeping it in perspective of the reader.
2. No. Often if it's not given, it's just a generic article they've doctored themselves which is easier to analyse than most actual newspaper articles. Why does it matter though?
3. Depends. Either you're not reading far enough into the technique to see how it relates to the contention, or the article is just badly written. Still, in either case, I can see cases where you could or wouldn't.
4. I'd still use the reader since other people can read it too. It's just that for example, parents would be the MAIN audience.
5. Of course. However, don't start making up names for these techniques. Teachers HATE when people do that. My teacher gave a list of ones she collated over a few years...quite hilarious to listen to really. And as for not naming, that's actually what you should be doing most of the time. You don't want to be too explicit in 'labelling' techniques.
6. From my understanding, exclusive language could most easily be identified just by the absence of inclusive language (e.g. 'we' should...)? Someone correct me if my understanding is wrong though...
7. Honestly they shouldn't be using past tense, and the title and type should be there. They might have lost marks here, and like I've said many times before, the high scoring responses are usually around an 8 or so - not full marks.
8. Looks like you're reading too far into it in my opinion. There could be plenty of other reasons why, and honestly, does anyone actually think like that? Even if that was true, it's just a formality in terms of structure, and not language that was used specifically chosen with the intention of persuading in the way you mentioned.