Combine 1/2 cup salt and sugar; rub onto all sides of roast. Wrap pork in foil; place in a shallow dish. Refrigerate overnight., Unwrap pork. Using a kitchen knife, scrape salt and sugar coating from roast; discard any accumulated juices. Transfer pork to a 6-qt. electric pressure cooker; add water. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 60 minutes. Let pressure release naturally for 15 minutes; quick-release any remaining pressure., Remove roast to a cutting board; let rest 15 minutes. Pour cooking liquid into a glass measuring cup and let fat rise to surface. Skim fat; discard. Reserve 1/2 cup cooking liquid; discard remaining cooking liquid. When cool enough to handle, shred meat with 2 forks. Place shredded meat in a foil-lined rimmed baking pan., Preheat broiler. In a small bowl, combine barbecue sauce and gochujang. Stir in brown sugar, vinegar and reserved cooking juices. Pour over pork; toss to coat., Broil 3-4 in. from heat until pork is crispy, 12-15 minutes, stirring occasionally. Combine mayonnaise, cilantro, lime juice and remaining 1/2 teaspoon salt; spread over cut sides of buns. Place pork mixture on bun bottoms. Top with lettuce, pickles, jalapeno and cilantro; replace bun tops.