Hi,
First of all i am disgusted with the people who you had the kitten from, kittens should not leave their mum untill it lest 8 wks. As a animal healer there are things to consider like emotional problems from leaving his mum to young, doe`s he bite and scratch in a playful or aggressive way. I would get him neutered at about 6 months, this will or should carm him down. But in the mean time when he`s biting and scratching stop having contact with him, and when he`s being nice praise him, so that he can learn the difference from being nasty and nice. I am just telling you in brief, but i hope you get the idea. Sometimes all animals need is understanding.