In a cup, combine chili powder, cumin, oregano, salt and pepper. Sprinkle half of the spice mixture over all sides of the pork. Set an Instant Pot to the high sauté setting and spray with a little zero-calorie nonstick cooking spray. Add pork and cook, turning until very browned on all sides, or 10 to 12 minutes. Pour lime juice into the Instant Pot and add garlic, jalapeño and remaining spice mixture. Set the Instant Pot to high pressure and make sure the pressure valve is in the "seal" position. Set timer to 35 minutes. Press start. Meanwhile, preheat oven broiler to high and position rack at the top of the oven. Cut the cabbage in half lengthwise. Peel leaves from each half, discarding the core, and wash & dry each cabbage leaf to use for the taco shells. When cooking is complete, allow pressure from the Instant Pot to release naturally (about 15 minutes). Use a slotted spoon to transfer the pork to a rimmed baking sheet and shred with two forks. Place pork under the broiler for 3 to 5 minutes to crisp up the edges. When done, remove, toss the pork with some of the remaining juices, then broil again for just 2 to 3 minutes this time. Serve hot, stuffed in cabbage shells. Garnish with toppings as desired.