Oh hon...it is so hard to know at this age! I agree that the scores seen a little low to MY definition of gifted but there is no standard numerical definition and there is no perfect test for every child.
The tester probably said 'gifted' for some reason.
It sounds like he is a handful to parent though! I think you will enjoy the book 'Transforimg the Difficult child Handbook.' It offers a way for parents to help Intense kids make the most of their gifts. That lower score on WM can be difficult for a kid. Sometimes it is a seperate issue and sometimes it is part of ADHD.
Best Wishes
Grinity