Preheat oven to 375 degrees. Make the crust: Coat a 9-inch pie plate with cooking spray. Pulse crackers in a food processor until finely ground; measure 1 1/3 cups, and discard excess. Pulse cracker crumbs, sugar, and 1/4 teaspoon salt in food processor to combine. Add butter, and pulse until mixture is moist and holds together when pressed between 2 fingers.
Press crust evenly into bottom and up sides of pie plate using the bottom of a dry measuring cup. (Make sure the sides and rim of the crust are firmly pressed so they don't crumble when pie gets cut.) Freeze for 30 minutes.
Bake crust until firm and turning darker around edges, 10 to 11 minutes. Remove from oven, and reduce oven temperature to 325 degrees.
Meanwhile, make the filling: Whisk together condensed milk, lemon juice, egg yolks and egg, and 1/4 teaspoon salt.
Pour filling into warm piecrust. Bake until center is set, 25 to 30 minutes. Transfer to a wire rack, and let cool to room temperature. Refrigerate for at least 3 hours.
Make the topping: Sprinkle berries with 2 tablespoons sugar and the lemon juice. Let stand for 30 minutes.
Meanwhile, heat egg whites and remaining 1/2 cup plus 2 tablespoons sugar in the heatproof bowl of a mixer set over a pan of simmering water until sugar dissolves and mixture is warm to the touch, 2 to 3 minutes. Transfer to mixer, and whisk on high speed until medium peaks form, 8 to 9 minutes.
Spoon berries over pie. Spoon meringue over top. Place pie under broiler, with rack in lowest position, until meringue is just browned. Alternatively, use a kitchen torch to brown the top.
Pie can be refrigerated overnight. Make meringue and berry topping just before serving.