Not sure the 5% is correct if all 5.7mln wagered was in NJ then correct but we know that isn't the case. Majority of that handle could be at 2.7% from out of state bets.
As far as 5.7mln for 16 races. The Longines Test Stake with just 5 horses, no show betting, and a .30 favorite handled over 3.3mln.