Universal’s/Blumhouse/Platinum Dunes threequel Purge: Election Year scored the most dough last night with $3.64M at 2,343 theaters; the biggest preview night for any Purge movie. This blew away Warner Bros./Village Roadshow’s The Legend of Tarzan which made $2.55M and Disney/Walden Media’s The BFG which grossed $775K. Even though tracking has both Tarzan and The BFG with an opening in the low $30Ms, some are expecting Purge: Election Year to surprise, and to be the best…