Preheat the grill to medium-high heat and brush the grate with oil or spray with nonstick cooking spray.
Rinse the shrimp and pat dry with paper towels. Sprinkle all over with salt and pepper.
In a small bowl, whisk together the Barbeque Sauce, apricot jam, 2 teaspoons vinegar and red pepper flakes. Toss two-thirds of the sauce with the shrimp, and reserve the remaining one-third for basting. Skewer the shrimp through the head end and the tail end, so the shrimp are skewered in two places, the top and the bottom.
Transfer the skewers to the grill. Close the cover and cook for 1 minute per side. Baste the shrimp with the reserved sauce, close the cover and cook until the shrimp are opaque and well glazed, 30 seconds per side.
In a medium saucepan over medium heat, combine the tomato sauce, 1/3 cup vinegar, molasses, ketchup, onion, brown sugar, ginger, salt and pepper, garlic and jalapeno, if desired. Simmer the sauce until slightly thickened, about 15 minutes.