Rinse and pat ribs dry. Remove thin membrane from back of ribs by slicing into it and pulling it off.
Stir together sugar and next 6 ingredients. Massage sugar mixture into rib meat, covering all sides. Wrap ribs tightly with plastic wrap, and place in zip-top plastic freezer bags; seal and chill 12 hours.
Bring sorghum and next 2 ingredients to a boil in a 3-qt. saucepan over medium-high heat, stirring occasionally; reduce heat to medium, and cook, stirring occasionally, 6 to 7 minutes or until mixture is reduced by half. Cool completely (about 30 minutes).
Preheat oven to 275°. Place lightly greased wire racks in 2 aluminum foil-lined 15- x 10-inch jelly-roll pans. Remove plastic wrap from ribs, and place ribs on wire racks. Cover with aluminum foil to seal. Bake 2 hours. Remove foil, and bake 3 more hours or until meat begins to pull away from bones, basting with sorghum mixture every 30 minutes. Increase oven temperature to 400°, and bake 10 more minutes or until ribs are browned.