I'm no spreadsheet expert, but shouldn't the +B value be outside the sum brackets. So cell N5 for DDD should read =sum(M5:M11)+B3 . Would that fix the total scores?
I have not dabbled in Google Spreadsheet, but why wouldn't the total be =sum(M5:L11)+B3? Empty cells have a default value of 0 and this would mean the total would automatically update as more scores are added.
Sidenote: When I was a brawler, I frequently checked the auction price of my competitors when I was looking at the standings. Would it make sense to insert a cost column between A and B?