This behavior is a bit different from teething. Teething in mammals happens when new teeth are growing in. Chewing helps ease the pain and discomfort that comes with having bones force their way out of your gums.
Birds don't have teeth, so they don't go through teething in this way.
Instead, their beak grows slowly and steadily, like our fingernails. For them, chewing helps wear down the beak and keep it a healthy length, and it will continues for their whole life.
They also use their beaks for much more than just "chewing", and what you're describing are actually an array of behaviors that will need to be addressed differently.
The headphone wires, blanket, and wall, are all "chewing" behaviors. They love to tear things down into tiny pieces. Our job in this case is to teach them what they CAN chew (toys, cardboard, etc.) and minimize their access to things they shouldn't. That may mean hiding the headphones and blocking off access to the wall. You'll also want to make sure they have acess to lots of good chewing options, and praise them when they use them. A toy that has been reduced to splinters is a success story. People get very creative with these sorts of things.
Chewing on YOU is a whole different story. What you're describing sounds like "preening", basically they're making you beautiful by removing any bumps or dots they think shouldn't be there. Baby birds don't know their own strength, so they need to learn that too hard hurts, and if they want you to accept preening, they need to be very gentle. Think about what a bird would do if they were preened too hard, and do the same. If they hurt you, squawk, set them down, and "fly away". (Walk away and ignore them for a bit). They'll learn.
For your breakfast, that's not chewing, it's just eating. Birds are social eaters, and they're also curious. If you're enjoying something, they're going to want to have some too. You basically have two options for this scenario, separate or roll with it. Personally, my birds often join me for meals. I give them a little piece of paper towel with either a small bit of my food (if it's bird-safe), or some of their own food, keep a safe treat, if mine can't be shared. They still try to get to mine sometimes, but mostly they're content to eat off their own "plate".
That, or I just eat where they can't get to me, usually by going in another room and shutting the door, or if it's near their bedtime, I'll put them in their cages to sleep and then eat my meal.
