I think the number one reason for his behavior is an attention need, and i know that need is more in tense with gifted children. I homeschool the older 2 and so often he is left out. I spent a good amount of time doing different activites with him today, involving him in cooking and cleaning. He was much better today. Only had 1 real issue all day that i can think of, dumped the baby powder out all over for Dad.
I bet the biggest thing i can do to improve behavior is to find more activites for us to do together , and involve him more spend time, that and make sure he gets enough sleep.
Also the behavior didn't start till after DS 3mo was born. So that's gotta show it's and attention thing.
I still need to check out the links. I'm a super busy Momma.

Took me so many time today to try to read through all your great posts.