Combine first 6 ingredients in a bowl. Reserve 2 tablespoons spice mixture. Rub remaining spice mixture evenly over pork, pressing to adhere. Heat oil in a large Dutch oven over medium-high. Add pork to pan; cook 15 minutes, turning to brown on all sides. Place browned pork in a 5- to 6-quart electric slow cooker. Add onion and garlic to Dutch oven; sauté 3 minutes. Add stock to pan, stirring bottom to scrape up browned bits. Remove pan from heat; stir in reserved 2 tablespoons spice mixture, ketchup, and vinegar. Pour stock mixture over pork in slow cooker. Cover, and cook on low 7 1/2 to 8 hours or until tender. Place pork on a cutting board; let stand 20 minutes. Skim fat from cooking liquid; reserve 1/4 cup liquid. Shred pork into large pieces, discarding bones and fat. Place pork in a bowl; add reserved 1/4 cup cooking liquid and salt; toss to combine.