The 72 hour quote comes from its having been discussed on the site here. As I recall, it is in one of his books. May have been something else he wrote.
[Sorry--I have had to excise a bunch of material here. It comes from material and possible discovery not yet on the record and that may be exposed to some leverage from the other side.]
Your other point is something to consider. She obviously wasn't in Kenya with her black dude for much longer that a few days between school terms because he was in school in Hawaii the rest of the year.
And I don't see the absence of pictures as particularly relevant either--1961? No digital cams; not many other pictures from her in that time frame; maybe she didn't take them.
I assume Stanley Ann was fairly tough--she didn't tell anything she didn't want them to know.
There is another possibility. Susan Blake's best testimony is in the video that was posted which was obviously made long after the fact. By then she and everyone else knew his birth location was a material issue and whoever prepared her pointed her to timing things to say.
Legally, it is pretty certain that he didn't become a citizen when he came down the shute if he was born in Kenya--so the record looks a little like an effort to establish a basis for claiming that he was born in the USA. That way, he doesn't need to worry about establishing his citizenship later? Doubtful anybody thought he was likely to run for President at that point.
Or anywhere else but the US. As you say, the law is clear on that. But that's just "citizenship", which is only necessary but not sufficient for "natural born citizenship".