A and C, first of all I agree with you that you have been treated wrongly. However don't you think it's a bit unfair to single out easyJet, an airline that up till quite recently never used to overbook its flights? Most established airlines overbook their flights and have done so for ages, that's nothing new.
Now your speedyboarding card. Speaking as a cardholder myself, this card does not give you more right to be on that plane than any other fare paying passenger.
So I am not saying it's right what happened to you, but this is they way things go sometimes in aviation as any frequent flyer can attest. Just make sure you get your compensation!