D.D.
This could be totally off base but:
He tried "I wanna please mom and dad" and that didn't get him a lot of attention. So now he's trying "I wanna give them hell" because maybe that will get some attention, even if it's negative attention.
I'm one of 4 siblings, and I love big families. But I also know that being 'the good kid' in a group of 4 often results in a child getting taken for granted and that good kid gets the least amount of attention. So as the mom in a family of 6, you do have extra responsibility to make sure you carve out one-on-one time with each child so they each feel special. Maybe life has been crazy lately and you are not doing that as much?
One suggestions: a rotating schedule of 'breakfast out with mom', where every Saturday, you take a different kid out for a one-on-one breakfast and devote all your attention to that one child for an hour. It's only once per month per kid, but I guarantee you that they will really look forward to it, and it may make a difference in your son's behavior if he's acting out because he's feeling overlooked.