It's not as uncommon as you might think for gratuity to be included in the price. I've heard of several times that's happened to people I know. If it's in the restaurant's fine print, or the way they do business (meaning it's posted somewhere, or shows on the bill you signed) then it's completely legal.
Stinks that your night was so terrible. Did you make the waiter aware of everything? If yes, then he should be fired for not doing whatever he could to make things better. If no, then there's really nothing to complain about and no reason to stiff him on the tip. Brought the wrong soup, but other than that, everything else was out of his/her hands (even the soup could have been out of his/her hands depending on who prepared it). I'm sure you did make him aware though, right?
As to not paying the bill, I don't believe that's possible either. Visa will tell you that you should have refused to pay it when it was presented to you. At this point, it's your word vs. the restaurant as to how your dining experience went, and you did give a credit card and sign the bill, so both the restaurant and Visa will be like "How bad could it have been? He signed the bill.".
Really stinks, and sorry it happened though.
Yes doctor, I am sick.
Sick of those who are spineless.
Sick of those who feel self-entitled.
Sick of those who are hypocrites.
Yes doctor, an army is forming.
Yes doctor, there will be a war.
Yes doctor, there will be blood.....