Take him back
Can you return this lonely unhappy baby 6 wk. kitten to whomever you got it from for about 3-4 weeks and then get him? It would be worth your while to offer to pay "board" even tho the person you got him from was ignorant in knowing what kittens need. He needs his mom to nurse on, as he is way too young to be taken away---11-12 wks. is an appropriate time to leave his mom and littermates. He needs his litter mates to play hard and roughhouse with for at least 3 wks. to learn to control his claws and biting. This is a very important part of his proper development. He will not understand spraying water in his face for crying for comfort of his mom and littermates and now you are their substitute...that would be cruel to spray him in his face.
You will have a much more balanced kitten if you take him back to person you got him from and then get him in a few weeks. Please consider this option for the sake of this baby.