Answer I would go with the nike and brooks sizing. I have a couple of brooks and the sizing seems the same. It's been a while since I've worn addidas so I can't give a comparison.
Answer Probably a 7
Answer Size 7 would probably work best for this item.
Answer I always wear a size 8 so it is hard for me to say. They are a tiny bit snug so I would go up on the size.