While I don't have specific examples from the book, there are some key reasons.
For 1, no one seemed to know in the books what Durin's Bane was exactly. Everyone who say the balrog were killed, and anyone of the Dwarves who did survive wouldn't have known what kind of creature it was. The wise such as Galadriel and Gandalf might have guessed, but they didn't know for sure.
Concerning Gimli in the movies not knowing about the fall of Moria. That was simply Jackson's move to not include why the Dwarves were there. In the books all 4 races had their own reasons for being there, and it just so happened to work to discuss about the Ring. Whereas in the movies they're all summonned to discuss the Ring.
So simply it was a change that Jackson made to not include all the details about the Dwarves reasons for being in Rivendell. In the books Gimli knew that Balin had went to Moria, but none of the Dwarves of Erebor knew what happened to Balin, just that no news had reached them for decades. So that way in the books Gimli thinks they might find news of what happened to Balin.
[COLOR=#0000cd][B]Eodread, Earendel, Isilmacil - Horizon[/B][/COLOR]
[B][COLOR=#ff0000]Thattickles, Thangorodread - Table Smashers[/COLOR][/B]