You definitely need assistance from a cat trainer here. Hopefully, someone will be able to give you tips. My cats are very gentle with the biting thing. Thank God for that!
I'm to the point that I'm thinking of taking a bath in the "Bitter Yuck" spray....kitten biting me now.
I watched a byte on TV years ago about a cat behaviorist saying to stop moving when kitty starts to play too rough. My cat starts to mouth me sometimes, but she knows what the words "gentle" "no teeth" and "be nice" mean, too. When my girl gets a little bit too rough and doesn't stop with the chewing when I tell her to, I stop and walk away from her. I'm no cat trainer and I got my cat as a full grown adult, but this little bit will work with my cat. She usually takes the hint that Mommy means business when I do this.