"Holding" isn't "wielding". A two-handed weapon requires only one hand to hold, but two to wield. You have to be wielding it for the feat to give you extra attacks of opportunity, which is what you are using the feat for I thought.No, PAM works because I'm wielding a Glaive.
Hold a Glaive and Attack with a dagger. Yes, Warcaster feat allows the Sorcerer do it. It can hold with one hand (Giant Glaive) and attack with off-hand weapon (Magical Dagger).