Does he throw his head up when you take off his halter? Or is it solely related to the bit?
After you've followed the advice that everyone else has given, maybe try this. It's completely out in left field, but who knows.
Just in his halter, work on having him open his mouth for you (like Sara described). Then, get a bridle with snaps at the bit ends. When you want to unbridle him, unsnap the bit (while still holding it). Then guide his mouth open (like you've been practicing) and remove the bit (be careful not to hit any teeth!) Then when you take off the remaining bridle, even if he tosses his head, there won't be any bit there to "punish" him. Then eventually, you can leave the bit attached and do the "Open Mouth-Remove Bridle-Remove Bit" all in one smooth motion w/o the head toss.
As for the bridling part...you said he takes the bit, but then tosses his head up when you try to slip the headstall over his ears. When I bridle, I hold the top of the headstall in my right hand, with my forearm resting on the horse's poll, between his ears, with the bridle dangling in front of his face. I then use my left hand to guide in the bit. If the horse's head goes up, he gets poll pressure from my forearm. If his head goes REALLY up, then my arm slides back down his mane and thus slipping the headstall over his ears. I'm not sure if this is already how you bridle or not. Looking forward to your video!