In a blender, puree raspberries, 1/2 at a time. Remove and set aside.
Puree cherries. Mix cherries and raspberries together, set aside.
Combine gelatin with rum extract and orange juice in a small bowl. Place bowl in a saucepan of hot water and stir mixture constantly until gelatin is dissolved (or microwave uncovered on low for 1 minute). Add gelatin, Equal and raspberry mixture to blender and blend for 2 minutes. Transfer to a mixing bowl, cover and refrigerate about 1-1/2 to 2 hours until mixture is set and sufficiently thickened to spread.
Soften gelatin in water 5 minutes. Stir dry milk powder into skim milk in saucepan. Heat to simmering. Add softened gelatin, stir until dissolved. Add vanilla and sugar.
Chill until mixture begins to thicken and ice crystals begin to form on sides of bowl. Beat with electric mixer until very thick and light, about 10 minutes.
To assemble: Split angel food cake into three layers. Place 1 cake layer on serving platter and top with 1/2 of filling. Repeat. Place last layer on top, frost cake with mock whipped topping.
Serves 12.
