Sounds like normal kitty behavior to me too. My vet won't neuter before 6months of age either, but you can find vets that'll do it earlier, although like has already been said, it's not going to change this behavior.
When he starts to play too rough, redirect to a toy or stop playing. My cats all love it when I roll up a small paper ball and throw it. They bring it back to me until they get tired of that game.
Now I never minded the biting and scratching that came with playing with them....long sleeve sweatshirts helped and I got used to having hamburger hands when they were kittens.
I can understand why a lot of people don't though, ha, ha.