And as regards the Deluminator question, perhaps, as you mentioned, this function was only added after Dumbledore became aware of his impending death, and realised the necessity of ensuring Harry’s quest would go smoothly, and therefore engineered this function (or activated it). And concealing it in an abject useful enough and with enough value that he knew Ron would carry it, is why he ???? put it in the Deluminator.
As for the ‘spy’ theory, I dislike it for several reasons. Whilst it is certainly possible, I find it unlikely Dumbledore would stoop to such lows, no matter what his interests. Because Dumbledore may have been manipulative and cunning, this would probably appear detestable to him, as it breaches the grounds of common decency. But the refutations you bought down are not particularly troublesome, should one choose to accept this theory. Dumbledore would act surprised and as if he was just finding out this information, despite already knowing it, as were he spying he wouldn’t wish Harry to suspect. And Dumbledore, as a highly gifted wizard, probably had numerous methods to find invisible objects, not to mention the plain common sense of Hagrid having obviously been talked to them, and they hiding in the most obvious place in the room.
Duke