While crust and crumb mixture are cooling, place sherbet and ice cream in refrigerator to soften. Scoop half of softened sherbet over crust; spread to cover crust. Sprinkle with 1/2 cup crumbs. Scoop all of softened ice cream over sherbet and crumbs; spread to cover. Sprinkle with 1/2 cup crumbs. Scoop remaining half of sherbet over ice cream and crumbs. Sprinkle with remaining 1/2 cup crumbs. Freeze until firm, 4 to 6 hours or overnight. Let stand 15 minutes to soften before cutting.