I actually read through that, and it still left me with the questions i had above.
Okay, I'll try to answer them
1. Do they basically have the memory of a gold fish, or do they simply choose not to hold on to memories and live solely in the present?
Their memory works just like any other human's, they just have no faith in the permanency of their memories.
2. Can they have lasting relationships, or is every meeting a first impression?
See above. They can remember things just fine, but they don't assume their memories will last forever. Because of this cultural belief, they tend to avoid making long range plans or commitments. They do live in groups of about 10-40 individuals.
3. Once they stop "perceiving" something, and it returns, do they make the link and know of this person or thing as they had known/met before?
Again, their memories work just fine, so yes. They would probably believe that they'd eventually forget that person.
4. The Abber language, as far as common/native tongues go, what is their grasp on speaking? How well do they speak common? What kind of accent or style would they adopt in their tongue and what could I consider a good reference point for their native tongue?
Their language is like no other language in the Ravenloft setting. The accessory
Carnival has an Abber NPC and he speaks no Common, and his native tongue is described as consisting of lots of clicks and whistles. Linguistically it would be a language with lots of
bilabial clicks5. Not really investing a whole lot of interest in the world around them, as they believe it's all a dream/nightmare, what's the level of knowledge they have about the lands outside the Nightmare Lands? What should I expect as I flit around Barovia and other places that are not my character's strange origins?
They have no knowledge of the world outside the Nightmare Lands. They are an aboriginal, nomadic society in an exceptionally harsh land, and thus do not have the luxury of schooling or travel.
6. How are they treated by NPC's in Barovia?
The same as anyone else that isn't Barovian.