Have you checked out some books/sites on parrot behavior?

An avian vet or behaviorist would be very good to give advice in this situation.

In the meantime....

My cockatoo will pick at any skin imperfections...that's natural preening to "help" you get that pinfeather that's stuck out...
She can be redirected though by scratching her favorite places or offering a toy.

The biting and ripping sound as if your bird is trying to be dominant. When he behaves that way, give a time out. Make sure his cage is lower than eye level to the humans...that gives him a subordinant place in the flock and may help him get the idea he's not the boss.

Birds are social but emotionally about equal to 2 year old humans. Be gentle, consistant, and firmly establish what you will reinforce and what will be a timeout...

Good luck and get professional advice as soon as you can. I am not familiar with the breed of your bird and sexual maturity often comes with temper outbreaks that need a certain sort of response that your vet can guide you through....