Since you have now had the car for a year and driven it for 12,000 miles, you do have to prove that the dual mass flywheel was either faulty or developing a fault on date of purchase and I don't see how you can do that for less than the cost of simply having it replaced. If you want to take the dealer to small claims using the evidence on the website that DMFs on Tiguans regularly fail you are welcome to do so, but I don't think that amounts to overwhelming evidence.