IMO he should pay taxes on the 90,000.00 from NBC as ordinary income (which I believe with his $900k win puts him in the top bracket of I think 35%), I think he can treat the first $10k from NBC as a gift (and tax free)... So, once you get that tax situation squared away, I think he's paying 20% on the winning from the track (which is better than his ordinary income rate of 35%)... unless of course he's got $900k in losing tickets
The best thing for this guy is that he lives in TX with no state income tax, so winning $800k on national TV shouldn't matter to his home state.