Preheat oven to 350°.
Grease 9"x13" baking pan and set aside.
Stir together graham cracker crumbs, butter, and ½ cup sugar in a bowl.
Press into 9"x13" baking pan. Set aside.
With an electric mixer, beat cream cheese, 2 eggs, and ¾ cup sugar until fluffy.
Spread cream cheese mixture over graham cracker crust in pan.
Bake at 350° for 20 minutes.
While the above is baking, combine 3 egg yolks, pumpkin, milk, salt, cinnamon, and ½ cup sugar in a saucepan. Cook over medium heat, stirring constantly, until thickened, about 5 to 10 minutes.
Dissolve the gelatin in the cold water and add to the pumpkin mixture.
Remove from heat and let the pumpkin mixture cool completely.
With an electric mixer on high speed, beat together 3 egg whites and ¼ cup sugar until fluffy.
Fold egg white mixture into pumpkin mixture and pour over cooled cream cheese layer.
Refrigerate until set.
Spread Cool Whip on top and refrigerate for at least 1 hour.
Cut into bars and serve.