Forced to move off the Fourth of July by “War of the Worlds,” 20th Century Fox fields its “Fantastic Four” this weekend at 3,602 theaters. Disney, meanwhile, counterprograms with its horror movie “Dark Water” at 2,657 locations. Even though “Four” is now facing off against the second weekend of Paramount and DreamWorks’ “Worlds,” there’s a bit of a contest for the No. 1 spot. The Steven Spielberg-Tom Cruise alien invasion film grossed $64.9 million over the Friday to Sunday portion last weekend, meaning a 50% second-week dip would put it around $32 million this weekend. Most industry estimates have “Four’s” opening slightly higher, but it could end up being close. Tracking on “Four” shows its audience is strongest among males, though it’s pretty even between those both over and under the age of 25.