I posted this a few months ago. Look at the 9th post in the thread. You have the exact same problem I had.
Caution on using a torque wrench on the oil drain plug
I think you over-tightened the plug like I did. I had the dealer replace the oil cleaner pan. I had the extended warranty, and although it really was my fault, Yamaha offered to pay for ("good-will") the part, which is around $100. I paid for the labor. I felt that was a reasonable compromise. I was prepared to argue with them about it, because the pan should never crack. Threads should strip out before it ever cracks the pan. My opinion, especially after hearing your story, is they have a design flaw there. The casting seam is a weak spot.
I might have tried replacing it myself if I could find the part cheap on ebay, but no luck. Since I have the YES, I really believe that should cover something.
You might want to try talking the dealer into giving you the part, because it should NOT have cracked. Especially if your bike is less than a year old.
Good Luck.