Then just watch and wait. If he/she is growing and feathering out well, he is probably fine and happy. I wouldn't worry about feathers hurting or anything else unless the need for sleep seems to increase. They should need less and less sleep as they mature.
I don't think it's his feathers bothering him. Growing feathers is a lot like growing hair, something that one doesn't really notice. All of the behaviors you describe sound normal to me, except the need for more rest than the other chicks. That is a nonspecific sign which could indicate any...