[question #1, right off the bat--why can't I spell "Nurture"?]
Chapter 5: IQ Tests for young kids are bogus. (Let's suppose, for the moment, that you beleive IQ tests aren't in themselves bogus.) How bogus? If you take 100 kids who measured gifted in kindergarden, only 23 of those kids would measure gifted in 3rd grade. (After that, IQ scores stabilize.) This matters because a lot of schools test for the gifted program in kindergarden, don't retest to let kids stay in, and don't have space for kids to enter when older. Their gifted programs aren't targeting the intended audience.
PersonallyI don't see any short-term relevance of this fact, but I have this sense that Helen is a late bloomer--one of those whose kindergarden ranking will be less than her third grade ranking. (Whatever those turn out to be.) She was slow to walk (and still physically clumsy), slow to take interest in books, can't pronounce words as well as kids a year younger than her...she's moving on her slower schedule. I really don't want to place her in too many situations where she'll notice this, because she might get it into her head that she's bad at X or Y or Z even though her badness is only temporary.
I don't think that's will be true of Erik.
Chapter 6: Siblings
Kids don't learn to be good friends from their siblings, it's the other way: they learn to be good siblings by having friends. (Since you're stuck with your siblings, it doesn't matter how you treat them.) Good sibling relationships aren't a question of how many fights siblings have, but how many good interactions they have. That is, siblings who play a lot together and fight some are going to be closer than siblings who mostly ignore each other and so never fight. This matters more than age difference, gender, and other similar factors. He also says that most kids fight are about possessions, but he bases this on a survey in which they ask kids why they fight, but I don't think kids would even notice if they were fighting over who is the best in the parent's eyes. One interesting note is that children's books about siblings are usually a negative influence, since even when the ultimate lesson is be nice to your brother, they usually show a lot of negative interactions with siblings first.
Personally I need to get a handle on the sibling thing. Helen is very affectionate towards Erik, but she's also very bossy (copying her parents, I suppose), takes toys away from him, and has hit him to get my attention. If anyone can recommend good books on fostering loving sibling relationships, send 'em my way. I already borrowed "Siblings Without Rivalry".
Chapter 7: Teen Rebellion
Teens are trying to be adults. Arguing with their parents makes for an improved relationship in their eyes, even when parents think it's destructive. Teens pretty much all lie to or otherwise deceive their parents, but a lot of times it's not because they want to avoid getting into trouble, it's because they want to maintain some privacy. The need for this peaks around 14 or 15.
Personally I'll let you know in ten years.
Erik is trying to type, so the rest will have to wait.