Combine 1 cup water and rind in a small saucepan. Bring to a boil; remove from heat. Pour into a large bowl; cool to room temperature. Add remaining 2 cups water, 4 cups juice, salt, sugar, and 1/4 cup soy sauce, stirring until salt and sugar dissolve. Pour salt mixture into a 2-gallon zip-top plastic bag. Add ice and pork; seal. Refrigerate for 24 hours, turning bag occasionally.
Combine marmalade, 2 tablespoons juice, and 1 tablespoon soy sauce in a small saucepan. Bring to a boil; cook 10 seconds or until marmalade melts. Remove from heat.
Preheat oven to 450°.
Remove pork from bag, and discard brine. Pat pork dry with paper towels. Place pork on a roasting pan coated with cooking spray. Bake at 450° for 15 minutes. Reduce oven temperature to 325° (do not remove pork from oven); bake an additional 45 minutes. Brush glaze evenly over pork; bake an additional 5 minutes or until thermometer inserted into thickest portion of pork registers 155° (slightly pink). Place pork on a platter. Cover with foil; let stand 15 minutes. Garnish with orange slices and parsley sprigs, if desired.
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