There isn't suppose to be a "official" anything in nxt, people at btt had at one point decided that the page count is getting massive and it is getting hard to be organised in that single thread.
But since all new updates of nrs clients are hosted there first, i assume that would be the next thing to an official website.
I can prove the balance amount at the time of forging by looking at the blockchain transaction history against the time stamp. And also compare the time stamp of forged block.
This should be enough.
EDIT:We now have one entry to my competition forging with only 10,007nxt! It's going to be hard to beat him!

For those still forging but have a higher balance, you still have a chance, but you have to lower your balance to less than 10,007nxt in order to compete against our current high(low)score, simply transfer some out to another account of yours, or do some good deeds like donation!