In a small bowl whisk the rub ingredients, and season the pork ribs evenly with the rub.
Prepare the grill for indirect cooking over medium-low heat (150° to 180°C).
In a medium saucepan combine the braising liquid ingredients and bring to a boil over high heat on the stove. Pour the braising liquid into a large grill-proof Dutch oven and place on the grill over indirect medium-low heat.
Grill the pork over direct heat, with the lid closed, until browned on all sides, 8 to 10 minutes, turning four times. Transfer the pork to the Dutch oven. Place the lid on the Dutch oven or cover tightly with aluminum foil. Cook over indirect medium-low heat, with the grill lid closed (keep the temperature of the grill as close to 150°C as possible), until the meat is fork-tender, 2¾ to 3 hours, turning the pork once every hour.
Using a slotted spoon, transfer the pork and onion from the braising liquid to a sheet pan and set aside to cool slightly. Keep the Dutch oven on the grill.
Increase the temperature of the grill to high heat (230° to 290°C).
While the grill is coming up to temperature, move the Dutch oven over direct heat and bring the braising liquid to a boil, with the Dutch oven uncovered and the grill lid closed, and cook until the liquid is reduced by about half, 5 to 7 minutes. Meanwhile, shred the pork and discard any large pieces of fat.
When the braising liquid is reduced, move the Dutch oven over indirect high heat. Pour off all but a few tablespoons of the braising liquid into a small bowl. You want to have just enough liquid remaining to coat the bottom of the Dutch oven. Add the shredded pork to the Dutch oven and cook, with the grill lid closed, until the edges are slightly crisp and caramelized, 10 to 15 minutes, stirring occasionally. As the pork crisps, drizzle it with the reduced braising liquid, 1 tablespoon at a time, to prevent it from drying out. You may not need all of the braising liquid.
Serve the shredded pork and onion warm in tortillas with salsa and lime wedges.