We've really been working on positive reinforcement with Kolby. It's something we figured out long ago: Kolby does much better, with his attitude, if he is praised for even the smallest achievements. He is such a completely different boy when he is happy.
He has noticed our focus towards happiness and positivity, and has been reacting in like manner. He happily (sometimes) does his chores and plays with his siblings. He takes turns better and he is starting to understand his triggers.
He even spent some time (willingly) reading a book. Mindboggling.
I hope this Kolby likes sticking around. He's pretty cool.