So incapacitate her, and put her in a room that blocks/scrambles outgoing signals. Open her up, and have your team of six super geniuses pull her apart.
Again, you're just assuming that would work. He can't be sure. As I've said, for all he knows they'd know something was wrong just because she missed a phone call.
That's just not true. Oda made it clear from the reaction in the early stages of the broadcast that most people of the world believe him at his word, because he is that highly respected among the general populace.
He said if his predictions didn't come true, that everything he says should be ignored. Most people also believe the WG, and ultimately they would listen to the highest authority in the world over him. He needed to stake his message on absolute certainty.
If he was concerned with the WG twisting his words and explaining it away, then I don't know why he made it a specific point to not lay the blame on any side. He wrote his speech exactly in a way where the WG could easily explain it away, and just say some pirates stole the Ancient Weapon and used it. He clearly didn't care about that happening.
He did that not to give the WG an out, but because he genuinely is agnostic about what their motivations might be, and also to not stoke a war against the WG in which countless civilians would be killed.
If he didn't want the WG to have the Mother Flame, why didn't he take any precautions to not let it fall into their hands after his death?
Because he believes in its existence as a form of free energy so he won't destroy or disable it, and he can't move it or York would know.
The spoilers say he wiped his memory only after two weeks, so he had to play pretend in that time.
True, I missed that. But still, if York can successfully act such that they couldn't tell, then so can they.
Again, really contrived, almost as if he had knowledge that the WG would just wait to kill him after he had time to create his broadcast rather than earlier, even though he's not supposed to have that knowledge.
He created the recording as soon as he found out about Lulusia. That's seperate from the memory wipe. But let's wait on the full summary/chapter before we argue too much about the timeline.
So he just assumed someone would pick up the torch and not only read the books, at risk of their life, but also disseminate that knowledge, instead of being proactive and doing it himself. He has a unique capability to send information across the world unimpeded, but he just trusts that it will work out after his death? Nah, I think that's silly.
The need to tell the world about the Void Century only becomes apparent because of Lulusia as I said. And after that, he did do it. As for the books themselves, he told no-one where Saul and the books are, not even Robin. The books need to remain hidden and protected for now, not disseminated.