Did you seek your lawyer's advise before taking the car back? Personally, i think you've made a big mistake taking the car back. The dealership DID acknowledge your car had vibration/shimmy problem and that's why they kept it in the shop for all these months. You should NOT have accepted the car untill it was fixed.
Also, you should have done a thorough inspection of your car and reported any damages/missing items, etc to the manager/foremen and refuse taking the car back untill the damage has being fixed and/or your missing items return.
I'm afraid the manager lied to you. He had a better chance fighting for you when the car was in his possession than now that it is in your possession.
You really need to sit down with your lawyer and straighten things out because now that you've taken the car back it is assume that you're satisfied with the condition the car is in.
If the dealership wanted their loaner back that bad, you could've jump into a rental and tell the dealership to either fix your car or replace it. You'll not accept the car untill the acknowledge vibration/shimmy problem has being fixed.
I don't mean to jump on you or be hash but i hate when people take advantage of nice people like you. The dealership and the rest of BMW reps recognized you were patient and kind so they ran over you.
Unless you have prove of your DVDs being in the car at the time you drop it off, i doubt you can win this one.
300kms is a lot of miles just for testing but looking at how long the car has being in the shop i can see the dealership making a justification for this.
You NEED to make this a legal issue in order for BMW HQs or BMW NA or NHSB or whomever the big people are to be aware of this problem.
If all these TOYOTA drivers have being nice and patient as you have being i don't think TOYOTA would've own up to any of these major issues.
Please fight on behalf for the rest of F01/02 owners having these vibration problems.
Good luck and may the gods be with ya