I have one that we got at 4 weeks (no mother cat or siblings and was dropped at the vet's I worked at), had to be bottle fed etc. She is my biter, only me though, but I'm the one that did all the work for the first several weeks. She has never even tried to go after anyone else and she is extremely social and wants to see everyone that comes in the door. She is much better than she used to be. I love her like crazy and she is a wild one to begin that always has a plan for what she wants to do and see how high up she can get on anything. Some cats are just really playful.
The main thing I do is, same as with dogs, a little yelp or quick high meow. She stops immediately. I think part of the problem is growing up without other cats until she was close to 8 weeks (couldn't introduce her to our others until we knew she was Feluk and FIV negative) meant she didn't learn good bite inhibition from other cats. So if you haven't tried, give yelping, crying out a try. It lets him know you he is hurting you. Also do it regardless if it hurts, but his mouth is on you so he learns that all mouth on skin is inappropriate. At the same time stop all of your movement and play and give him a break for about 20-30 seconds and then you can resume activity.
I have many nighttime player cats that went after my legs, lol. I usually just removed them from the bed each time and they would get the message, if I play I can't be on the bed. You can try having a toy, so if he goes after you, throw the toy off the bed if he will chase it and keep him occupied. Have several toys ready each morning.