Heat oven to 375o. In a bowl, combine graham cracker crumbs, 3 tablespoons sugar, butter, and salt. Press into buttered pie plate; bake until ightly browned, about 12 minutes. Cool completely on a wire rack. Reduce oven temperature to 325o.
In a bowl, combine condensed milk, yolks, and lime juice. Pour into crust.
Return pie to oven and bake until center is just set, 15 to 17 minutes. Cool completely on wire rack.
In the bowl of an electric mixer, whisk together remaining sugar and egg whites. Place bowl over a pot of simmering water, and stir until warm to the touch and sugar is dissolved. Place bowl on mixer fitted with whisk attachment, and mix on medium-high speed until stiff peaks form and meringue is glossy, about 5 minutes.
Place cream in a chilled bowl; whisk until soft peaks form, being careful not to overmix. Gently whisk a third of the cream into meringue. Using a rubber spatula, fold in remaining cream.
Top pie with meringue; freeze just until topping is firm enough to slice.