Prepare Citrus Compound Butter: Stir together all ingredients in a medium bowl until blended.
Prepare Turkey: Preheat oven to 325°. Remove giblets and neck, and rinse turkey with cold water. Drain cavity well; pat dry. Loosen and lift skin from turkey with fingers, without totally detatching skin; spread compound butter underneath. Carefully replace skin. Sprinkle cavity with 1 Tbsp. salt. Squeese citrus halves into cavity; place squeezed fruit, celery leaves, and next 2 ingredients in cavity. Tie ends of legs together with string; tuck wingtips under. Place turkey on a roasting rack in an aluminum foil-lined roasting pan, breast side up. Pour broth in bottom of roasting pan.
Prepare Glaze: Place 1/2 cup unsalted butter, marmalade, and honey in a small saucepan. Cook over medium-low heat until butter melts. Remove from heat; sitr in salt and next 4 ingredients. Brush half of glaze over turkey. Loosely cover turkey with foil.
Bake at 325° on lowest oven rack for 1 hour and 30 minutes. Uncover and brush with glaze. Bake 1 hour and 25 more minutes or until a meat thermometer inserted into thickest portion of thigh registers 165°, basting with remaining glaze every 30 minutes. Shield with aluminum foil to prevent excessive browning, if necessary. Remove turkey from oven. Let stand, covered with foil, 30 minutes.
Place turkey on a serving platter, reserving drippings in pan. Pour about 1 cup pan drippings into 1-cup glass measuring cup. Let stand 10 minutes, and skim fat from drippings, reserving 1 Tbsp. fat. Heat reserved 1 Tbsp. fat in a small saucepan over medium heat; whisk in flour. Cook 1 minute. Gradually add 1 cup reserved drippings, whisking constantly. Cook 5 minutes or until thickened. Add salt and pepper to taste. Garnish turkey, if desired, and serve with gravy.