Crust: combine wafer crumbs, sweetened coconut and melted butter. Mix well. Press mixture evenly over bottom and sides of an 8 or 9 inch pan. Chill.
Filling: mix gelatin and 1/2 cup sugar in saucepan. Add pineapple juice. Let stand until gelatin has softened. Place over low heat; stir until gelatin dissolves. Remove from heat. In large bowl, beat egg yolks well. Gradually beat hot gelatin mixtures into egg yolks. Let cool.
In medium bowl, beat cream cheese until fluffy. Add to gelatin mixture; beat until well blended. Stir in rum and coconut extract. Refrigerate gelatin mixture to chill. Stir frequently as mixture thickens. When gelatin mixture is consistency of unbeaten egg whites, remove from refrigerator.
In large bowl, beat egg whites until foamy. While beating, add remaining 1/4 cup sugar, 1 tablespoon at a time, until whites hold stiff peaks. Fold egg whites into thickened gelatin mixture. Turn into prepared crust. Refrigerate for 6 hours or as long as overnight.
Topping: combine crushed pineapple, 2 tablespoons sugar and cornstarch in saucepan. Stir until cornstarch dissolves. Cook over medium heat, stirring, until sauce boils and thickens slightly. Chill. Spoon sauce over top of cheesecake.