Well, I wouldn't storm in there with the keys to the car, and drive it right out with the bodyshop people runnin' along tryin' to stop you :p Seriously, any bodyshop which has been around for a while must at least provide a minimum quality of acceptable work. If the problems are VERY obvious, and even the bodyshop manager can see it for himself, and acknowledges it himself, and simply says, "that is the best we can do," then there is something REALLY wrong. Did you ask him WHY it was the best that he can do? I mean, painting a Mercedes, is no different from painting another car...this is not merely a little difference in tint...it is a very obvious non-shiny shade that can be seen and it is peeling under your finger nails in some spots...this is kinda...uh...pathetic, don't you think?
Did you have a look at some of the work the bodyshop had done before? What did it look like? I cannot believe ANY bodyshop can do such a horrible job and stay in business...simply explain to him you are upset about the work, point out the problems, and say the quality of work is unacceptable. Say they will either redo the work, or refund your money and you will take it to another bodyshop. Say this with a serious, calm tone. If he just shrugs and says, "it is the best I can do, I want the other half of my money," then tell him that the work is not completed to your satisfaction, there are obvious faults, and say you will speak to your lawyer and just leave the car there. You must have signed a paper sayin' that with satisfactory completion of the job, he gets the second half of the money...isn't this the point of putting down money in the front, then giving the rest in the end? Take some photos of the job, showing the obvious problems, take it to a lawyer, and see what is the next step to take. If this is an insurance claim, and the job is bein' paid for by your insurance, I am sure the insurance company can get involved. I am not familiar with all the legal avenues and the cost/benefits of actually pursuing it and if it is actually worth it, but the problems you listed are quite unacceptable...
1995 black pearl/black Mercedes-Benz E420