Combine first 3 ingredients, mixing well.
Press flour mixture into a 13- x 9-x 2-inch baking pan.
Bake at 350° for 30 to 35 minutes, cool completely.
Combine cream cheese and powdered sugar, beating until fluffy, fold in 1 cup whipped topping.
Spread over crust.
Combine 1/2 cup sugar, gelatin, ginger, cinnamon, and nutmeg in a large saucepan.
Combine egg yolks and milk, add to saucepan, and cook over medium heat, stirring constantly, until mixture boils.
Stir in pumpkin, 1 teaspoon orange rind, and orange juice.
Chill mixture until partially set.
Beat egg whites (at room temperature) and 1/2 cup sugar until stiff peaks form, fold into pumpkin mixture.
Spread over cream cheese layer.
Spread 2 cups whipped topping over pumpkin layer.
Chill thoroughly.
Garnish with orange rind.