Place roast in a 3-qt. slow cooker. In a small bowl, mix 1/3 cup mustard, brown sugar, garlic powder, cayenne and 1/4 teaspoon salt; brush over pork. Add broth; cook, covered, on low until meat is tender, 6-8 hours., Meanwhile, preheat oven to 400°. Scrub potatoes; pierce several times with a fork. Bake until tender, 45-50 minutes., Place coleslaw mix in a large bowl. In a small bowl, whisk yogurt, mayonnaise, vinegar, celery seed, garlic salt and remaining mustard and salt; pour over coleslaw mix and toss to coat., Remove roast; cool slightly. Shred pork with 2 forks; return to slow cooker., With a sharp knife, cut an "X" in each potato. Fluff pulp with a fork. Using a slotted spoon, place pork mixture and coleslaw over each potato.