Using fingers, work crumbs and 3 tablespoons sugar into melted butter. Divide mixture, using 2/3 to cover bottom and sides of 9-inch springform pan and reserving 1/3 as topping to sprinkle over filling. Dissolve gelatin in boiling water. Set aside until syrupy. Combine milk and cream and beat until mixture is quite thick. Mix cheeses, lemon juice, vanilla, salt and 1/2 cup sugar in separate bowl. Add cheese mixture to cream mixture. Blend in partially set gelatin. Pour into crust and chill 4 hours.