just wanted to stir the pot and throw in another thought on Question 1:
The "Call" is clearly a supernatural occurrence. Chalking it up to
coincidence is stretching way too far, even for someone who likes to find
mechanistic explanations.
But if you set yourself the task of finding the least supernatural explanation,
then I would suggest Aragorn as the best answer.
Eru or the Valar are clearly "extremely" supernatural entities, so I discard
them immediately as not fitting the "least supernatural" criterion. I
acknowledge the excellent arguments for Gandalf (primarily that he's done this
before, with Frodo at Amon Hen, and however many times he's done it to summon
Shadowfax). However, at this time, he cannot reasonably be sure that
Frodo is even alive, and if so, where they are--the last he's heard of them,
they were going to attempt the pass of Cirith Ungol. Finally, as a Maia,
even an incarnate one, he's still too supernatural to fit the bill for "least
supernatural".
Which leaves us with Aragorn. We might not expect that a mere mortal has
telepathy, but we are saved by Acathalion's post: apparently, closeness,
authority, and urgency are the only requirements. Aragorn is certainly
close to the hobbits, he has rightful authority, and he certainly has the
urgency. Moreover, with the palantir, he could have been scouring Mordor
in search of them all during their march, finding them at last on the morning
of the 25th (just before his meeting with the Mouth), and wishing them godspeed
with all his heart. And with all the criteria from Acathalion's post, his
thoughts took wing.
And it just occurred to me that if he had indeed found Sam & Frodo just before
the meeting with the Mouth, and had told Gandalf, that would be yet another
explanation for how he and Gandalf played it so cool with the mouth.
Question 2:
Juxtaposing Frodo's suffering with a child piggy-backing in the Shire creates
dissonance that unpleasantly emphasizes how much he's been reduced to.
It's worth noting that that's already apparent from the night before, when he
was shivering from pain and cold, and needed to be cradled like a baby to find
relief.
