I'd say that the kins (rather than races) have their own languages but that a common pidgin => creole type of language is pretty strong in the lands due to the historical mixing of kins. There are probably several dialects due to the isolation during the Blood mist. Concerning written language I think it is stated somewhere that the Orcs have no written language of their own.
To me it seems reasonable that the dwarves have some kind of dark vision since they often dwell underground. Wouldn't it be cool if dwarves were able to emit short burst of infrared (invisable to men) stroboscopic light from glands by their noses every five minutes or so? The reflections give them a snapshot of the surroundings paired with a very good visual memory that lets them keep that image until the next flash. It would give dwarves limited dark vision that would limit their mobility in darkness as well as awareness of changes or movement. The light bursts might scare some beasts and attract others that prey upon dwarves. The lenght of the dark period between bursts might depend on for instance WITS.