Sorry, this still doesn't help you. You can't run the XeLL loader (KK disc) without already knowing your DVD key. And even if you could, I can't believe you're eager to attempt this after failing already at such a relatively simple effort.
Here's a suggestion that will save you much heartache next time. Since you already have a BenQ drive on your hands, use it for your next attempt at modding. Get another BenQ system and don't even attempt to flash it. Just read the firmware from that drive, then mark it "good" with the current date and set it safely aside. Now flash the other drive, and test it in your 360. If you did everything correctly, you're golden. If you still screwed up somehow, you needn't worry, since your "good" drive is untouched. The next time iXtreme is updated and you need to flash again, take the drive from your 360, mark it "good" with the current date and flash the other drive this time. With one working drive always set aside for safekeeping, that's extra protection against ever losing your key or shooting yourself in the foot again.