Nice to see a thread bump here...yeah I think it's one of the best rock performance DVD's out there myself. They are flawless in this and this is proof that Dennis competes the proper chemistry.
As far as shakin' his head at Tommy at the beginning of Fooling Yourself? I don't know. It does look that way doesn't it. Seems to be a "whatever" at the show Tommy is puttin' on...or...it could be an emotional nod to the melody of the song in general or at his own fingering.