Whisk the instant pudding mix and cold milk in a medium bowl for about 2 minutes, until thickened. Let it stand for 5 minutes to set.
In a separate cold bowl, beat 1 cup heavy cream with the powdered sugar and vanilla until medium peaks form. Refrigerate until needed.
Stir the cooled coffee and rum or coffee liqueur together in a small bowl. If the apricot preserves are very thick, stir them until smooth enough to spoon in small dollops.
Place the chopped chocolate, 1/3 cup heavy cream, and salt in a microwave-safe bowl. Microwave in 15-second intervals, stirring after each interval, just until smooth. Let the sauce cool to room temperature; it should be fluid but not hot.
In a 3-quart trifle bowl or deep serving dish, arrange half of the vanilla and chocolate pound cake cubes in an even layer. Spoon over half of the coffee mixture, using just enough to lightly moisten the cake without making it soggy.
Top the cake with half of the pudding, half of the apricot preserves in small dollops, half of the walnuts, and half of the raisins. Repeat with the remaining cake, coffee mixture, pudding, preserves, walnuts, and raisins.
Spread the whipped cream over the top. Cover and refrigerate for at least 2 hours so the layers soften and the flavors blend.
Scoop the chilled dessert into individual bowls. Drizzle each serving with the chocolate sauce just before serving.