Outside food or drink is not permitted, but you can buy food at the concession stand, assuming the concession stand is open.
AMC’s pricing is in line with what Cinemark offers with their own private theater program, which I tried out a couple months ago.
Following the lead of competitors like Cinemark, Alamo, and others, AMC Theatres announced today that it was starting a “Private Theatre Rentals” program.
You can’t just watch whatever title you want; the options are limited to the ones that AMC is offering.