Soften gelatin in cold water in a large mixing bowl 5 minutes. Add boiling water and 3/4 cup sugar, stirring until gelatin and sugar dissolve. Stir in orange rind, orange juice, lemon juice, and salt. Freeze until slushy, stirring occasionally.
Beat whipping cream in a medium mixing bowl until frothy. Gradually add remaining sugar, beating until soft peaks form. Set aside.
Beat egg yolks in a small bowl until thick and lemon colored. Beat egg whites (at room temperature) until soft peaks form. Fold egg whites into yolks. Fold egg mixture into whipped cream. Fold into orange mixture. Spoon into three 2-cup metal ice trays (with dividers removed). Freeze until firm.
Cut into squares or scoop out with ice cream scoop, and place in sherbet dishes.