Brock, Misty, Dawn, May
Yes you can get other Pokemon that arent in pearl.
Pokemon crater
There is no other place to get it besides Mount. Coronet. Sorry
no
No, sorry.
Growlithe, Staryu, Oddish, Pichu
No, just Unown.
ice
Smogon is a great Pokemon site, Pokemon Marriland is alright for other things too. There is also the Official pokemon site
Im pretty sure there are no other uses besides selling them.
Consonants
As far as I know there is not other way besides using wi-fi or trading.