Yeah, me too. My nan used to nurse loads of birds back to health - she saved a robin once, and after that it kept trying to get back into her house to get at the meal worms :P
Maybe, but none of the other birds did. I've heard about robins being more confident then other birds. There are a lot of stories I've heard of wild robins coming in through cat-flaps and stuff to get food if they know it's there. It probably considered the house as part of it's territory.
He could have fallen from the nest. The fact the mother is still feeding him suggests that she hasn't sensed anything wrong with him. He should be ok, if a cat doesn't get him :p
