Preheat oven to 350°F. In a small bowl stir together crushed graham crackers, pecans, flour, sugar, salt, and the ⅛ teaspoon cinnamon; stir in melted butter. Spread in a 9x9x2-inch square baking pan. Bake for 10 minutes, stirring twice. Cool completely.
In a large bowl stir dried egg whites into the warm water; whisk with a fork. Let stand for 2 minutes. Beat with an electric mixer on medium speed until the dried egg whites are dissolved and mixture is frothy. Add lemon juice and cream of tartar. Gradually add powdered sugar, beating on high speed until stiff peaks form (tips stand straight).
In a medium bowl stir together pumpkin, yogurt, pumpkin pie spice, and the ½ teaspoon cinnamon. Gently fold egg white mixture into pumpkin mixture. Fold in the whipped topping.
Lightly coat a 9x5x3-inch loaf pan with cooking spray. Sprinkle ⅓ cup of the graham cracker mixture in the bottom of the loaf pan. Spread 4 cups of the pumpkin mixture evenly over the graham cracker mixture. Evenly sprinkle the remaining graham cracker mixture over the pumpkin mixture in loaf pan, pressing in slightly. Top with the remaining pumpkin mixture, spreading evenly. Cover with plastic wrap. Freeze for at least 4 hours or up to 24 hours.
To serve, invert onto a chilled serving platter. Let stand at room temperature for 30 to 60 minutes before cutting into slices.
Tips: Sugar Substitutes: Choose from Splenda Granular or Sweet'N Low bulk or packets. Follow package directions to use product amount equivalent to 1 teaspoon granulated sugar. Nutrition Per Serving with Sugar Substitute: same as below, except 132 calories, 18 g carbohydrate