It sounds to me that he has not learned to really control his emotions and temper.
I think the most important thing for you to do is to model to him how you stay calm and in control. So in the midst of an incident you might say "ds1, I am feeling extremely shocked and angry and hurt that you have just thrown toast in my face, and my instinct is to shout and scream, or to throw toast back at you. But I have learned to control my emotions, and instead we are going to have a calm discussion about this."
i.e. absolutely under no circumstances must you or your lose your temper with him.
Sit him down and have a calm and reasoned discussion with him. Ask him how he thinks you feel when he behaves in this way. Ask him how you feel when you pick him up from school and are told of his star prize or whatever. Then tell him that this contradiction leaves you very confused.
I would set up a positive reward scheme (just because this is what works with my boys). So rather than banning PS2 and TV or whatever, I would say he can earn the right to 30 mins PS2 or 30 mins TV by doing x, y, or z.
For example for not being rude or hurting any of his siblings in the morning before school, etc.
Does he have chores and responsibilities at home? If not, set him some: that should stop him being so cocky. Give him some responsibilities too, and get him preparing meals for the whole family and himself.
Hope some of this helps.