New Cat Is Super Energetic, Bitey, Always Hungry, Play Aggressive

A more energetic cat would need more than the suggested amount of food because he'd be burning off more calories.

I got my Monkey at 6wks (from vets office that couldn't save the mom). My adult cat had no teeth so Monkey didn't learn biting hurt. At a yr old we got a kitten. Within 2 wks Monkey started biting gently. So another young cat/kitten could help not just with biting but with running off some energy.

Ah! You got di and bob here! this is very good advise, I would follow it completely!

pay special attention when di and bob said you have to do it every time!
every time you skip you start over

scruffing an adult cat can be dangerous, personally I'd never treat an adult cat like this

You don't scruff hard, you just gently grab and hold down for 2-3 seconds
and you don't lift them off the ground.