I've been trying to do it as fire main also but I was stuck for so long. I started changing my main and trying other guides just for the sake of passing this exam and still wouldn't work UNTIL TODAY. I finally passed it as wind main. If you're willing to change to wind main for one day to pass it here is the guide that helped me.

https://www.youtube.com/watch?v=DJcFqx1NWWU

I passed it with 27.9k power, a bit lower than the power in the video. The only difference from that video was that guy died for me before I could use his mystery on kakashi but I was still able to win with him dying early. It took me about 3 tries to get this done. Glad I finally beat this * exam :@.
If you can't change into wind main then sorry and good luck :/