I think 14 weeks is too young to be spayed/neutered. Our vet wouldn't neuter our older cat until he was at least 5 months old. Check with your vet though, as they may have a different age requirement for neutering.
He is a kitten, so it's in their nature to be a bit wild, playful and bite sometimes. You can use a spray bottle and spray him with water when he bites, that may help.