Seems to me that he has everyone running round in circles, and he is enjoying it. He is the centre of everyone's attention - what fun!! Take away the fuss and you take away the fun.
I recently had to look after a young relative for a few days. She would always take ages to get ready to go out - nag, nag, nag, and she would still be sitting there. Until I got fed up with it, and instead of nagging her to get ready I got a book and sat on the sofa reading. There was a long silence until she asked what I was doing and I said I was waiting for her to get dressed, but meanwhile I was making good use of the time by reading. And she said - "but you haven't nagged me yet!" To which I replied, "no, can't be bothered any more, if you get dressed we will go out and if you don't I am quite happy reading. I can sit here all day," Ten minutes later she was dressed and ready!!
I am not saying this will always work, but a complete turnaround from your usual reactions can sometimes work wonders.
Another idea - a friend of mine got fed up with her stroppy son, and the way that stopping him doing things as a punishment never seemed to work. So instead of stopping him doing things, she stopped doing things herself. For instance, after one particularly difficult outburst, dinner was a cheese sandwich because she refused to cook. On another occasion she left all his favourite snacks off her shopping list; on another occasion she "forgot" to wash his favourite tshirt. No comment, no explanation, no argument - and she says that he is slowly learning that his lack of cooperation will mean a corresponding lack of cooperation on her part.
Some other things occur to me - have you had his eyesight tested? Is he having difficulty seeing things?
You say he is very bright - how bright? Is he maybe just bored because he is very intelligent?
Whatever it all is, hope something said here might help. Good luck!!