This I agree with. We're clearly meant to assume Elan's mother is alive, and that should be all that's relevant to discussion. And yeah, I don't see much use in saving info on some 'strong female characters are coming up'. It's temporary at best, like "How long will the break be."
This one, I think, is not a joke, however. I mean, he added ludicrous precision as a joke, of course, but ~70% is precisely where we should be right now, based on what he's said in the past (that we were past the halfway point at the end of Book 4) and what he's said about how much longer there is (at least three years. We're at over ten years right now, and if you assume a fifteen-year run, say, we're at the 70% mark now.)
I'd agree if Rich was the kind of author to stat out his characters fully and iron out their abilities beforehand, but he's said that he leaves gaps specifically so he can make jokes or impact the plot as he needs to later on. It would not be outside the line of reasonable thought to assume that he doesn't have the world set in stone to a further degree than the number of continents and vague ideas of the kind of climates and races found on each. If he really does have the whole OotSworld mapped out as extensively as we've seen here, then to be honest I am a bit surprised.
I mean, it makes sense. I just think it makes sense to think otherwise, too.