Preheat a grill to medium high. Cook the bulgur as the label directs; drain well, transfer to a large bowl and set aside.
Whisk 2 tablespoons olive oil, the juice of 1 lemon, the garlic and paprika in a small bowl. Butterfly the pork: Slice lengthwise down the center, stopping about 1/2 inch before cutting all the way through. Open the pork like a book and flatten slightly with your hands. Lay a piece of plastic wrap on top and pound with the flat side of a meat mallet or a skillet until 1/2 inch thick; discard the plastic wrap. Transfer the pork to a shallow baking dish; season with salt and pepper, then rub all over with the garlic oil. Let sit 10 minutes.
Brush the grill grates with olive oil. Grill the pork until well marked, about 6 minutes per side. Transfer to a cutting board and let rest.
Add the remaining 1/4 cup olive oil, the juice of the remaining lemon, the vinegar, watermelon, mint and scallions to the bulgur; toss and season with salt and pepper. Slice the pork and serve with the watermelon tabouli and lemon wedges.