1) I can't think of much beyond what was pointed out in the question. Rivendell
is a place to rest and recover, and also a place to plan the journey ahead,
seek advice and check the maps.
2) Well, I'm afraid that I would have been horribly shy and insecure amid all
those strange dwarves and elves, but Frodo seemed to do just fine. He and Gloin
had Bilbo's adventure in common to talk about, and Frodo had occasionally
encountered Dwarves back in the Shire. Perhaps that accounted for the seating
arrangement. Also, I wouldn't be surprised if Gandalf and Elrond had people
looking out for Frodo should be become ill or unduly upset for some
reason.
3) The “fading” of the Elves from Middle-earth is emphasized in LOTR. The
fate of the Dwarves is not discussed as much. Are we seeing a hint here
that the Dwarves are also fading? As others have said, the Dwarves seem quite
successful and prosperous. I see not so much a "fading" as a finger of the
Shadow that threatens
Middle-earth.
*******************************************************
Although now long estranged, Man is not wholly lost nor wholly changed.
Dis-graced he may be, yet is not de-throned,
and keeps the rags of lordship once he owned:
Man, Sub-creator, the refracted Light
through whom is splintered from a single White
to many hues, and endlessly combined
in living shpes that move from mind to mind.
Though all the crannies of the world we filled
with Elves and Goblins, though we dared to build
Gods and their houses out of dark and light,
and sowed the seed of dragons--'twas our right
(used or misused). That right has not decayed:
We make still by the law in which we're made!
