I can't answer #1 because I've always used the standard BB.
Don't use a carboy brush on the BB - clean by filling with an Oxyclean solution and let it sit overnight - if you need to scrub the inside, leave a little Oxyclean solution in the bottle and put a washcloth into the bottle -swirl it around and let the cloth do the scrubbing - this way you won't scratch it.
Be sure when aerating not to rock the BB on its edge - see the Better Bottle web site for their technique of using a tennis ball under the center of the BB to avoid the stress cracks that can be caused by tilting the bottle on its edge.
Look under Product Information - How_To Tips
I think they do provide a pretty good oxygen barrier, though not as good as glass. I've left my beer in them for several weeks with no problem, but if I were going to age one for months I would use glass.
Edit: I forgot to answer #2 - you can use a standard 3 piece airlock with the proper size bung