Mix graham crackers, 1/2 cup sugar, and 1/2 cup butter. Press firmly on the bottom and sides of a spring form pan. Reserve 3/4 cup for topping. In the top of a double boiler, beat the egg yolks with the sugar and salt. Stir in milk and place over simmering water. Cook, stirring constantly, until mixture is creamy. Add the gelatin and stir until gelatin is completely dissolved. Mix in the cottage cheese, whipping cream, and pineapple. Fold in stiffly beaten egg whites. Sprinkle remaining graham cracker mixture on the top. Pour into crust and chill until firm.