To make the pork, cut the pork roast into medium (2 to 3 inch) chunks. Put the pieces in a large slow cooker (at least 5 quarts).
Mix the salt, paprika, sugar, garlic powder and onion powder. Sprinkle over the meat, turning the pieces to coat evenly.
Cover and cook on high for 5 to 6 hours or on low for 8 to 10 hours, until the meat is pull-apart tender and reaches an internal temperature of 190F.
Using tongs and a slotted spoon, transfer the meat to a rimmed platter or baking sheet. Let rest until cool enough to handle. Pull the meat into strands. It should shred very easily.
When the pork is almost done, make the sauce. Bring the ketchup, vinegar, Worcestershire, garlic, habaneros and hot sauce to a boil in a small sauce pan over medium heat. Simmer for 3 minutes.
Mix the dark brown sugar, paprika, black pepper and celery salt together in a small bowl. Add to the ketchup mixture and mix well.
Slowly add 1/2 cup water to bring the sauce to the consistency you like and taste.
Pour the sauce over the shredded pork. Place back in the crock pot on warm just long enough to heat through. Serve on buns.