I'm pretty much in the same boat as you I have a 12 week old male Yorkie who loves to play with me! He bites but he is not trying to hurt me! If I feel his is getting to aggressive I'll stop him & say ow! He licks my hand after that! They are very smart dogs & I know Jax is such a sweetheart! You just have to let him know it hurts even if he isn't hurting you very badly....I know they love to make us happy & will never want to hurt us! You've got to train him & just make sure to let him know when he needs to ease up!
Good luck & have fun!