-and if you never let me go

dnot say retarded i am sure they are fully capable and with the ability to reason with neurotypical ability for their age and social status, perhaps they make strange choices from time to time or small mistakes like forgetting keys and standing out in the cold and flip-flops but this is only the one of them, nick is just a freeloader and perhaps crafty for that very reason and you cannot discount him nor ascribe any mental challenges to him for he simply does not face those problems in his life from day to day