Stir together first 3 ingredients in a bowl. Cover and chill 20 minutes.
Remove fruit from bowl with a slotted spoon, reserving syrup mixture.
Brush pound cake slices with syrup mixture. Arrange half of slices in bottom of 4-quart bowl or trifle bowl. Top with half each of mango mixture, banana slices, Coconut Cream Custard, coconut, and macadamia nuts. Repeat layers.
Beat whipping cream until foamy; gradually add sugar, beating until soft peaks form. Add vanilla; beat until blended. Spread evenly over top of trifle. Cover and chill 1 1/2 hours. Garnish, if desired.
Note: For testing purposes only, we used Malibu Caribbean Rum with Coconut Flavor.
*1 (24-ounce) jar refrigerated mango, drained and cut into 1/2-inch cubes, may be substituted.