Trim the pork of any excess fat. Spread chopped onion onto the bottom of the slow cooker. Place the roast on top of the onions. Add chicken broth.
Cover and cook on low until the pork roast is very tender and shreds easily (about 8 hours). Remove the meat to a wooden cutting board. Shred the meat using two forks, removing any fat or grizzle. Skim any excess fat from the liquid in the slow cooker.
Return the pork to the slow cooker and mix with BBQ sauce. Keep warm.
To make the coleslaw- in a large bowl mix together the mayonnaise, sugar, salt, pepper, celery seed, garlic powder, onion powder, and cider vinegar. Toss coleslaw mix with dressing to coat. Chill for at least 1 hour before serving.
Lightly grease the grates of an outdoor grill (or indoor grill pan). Heat the grill to medium-high heat.
Add the hot dogs and cook while turning until they are heated through and have nice grill marks. Place the hot dog buns, cut-side down onto the grill and cook until lightly toasted.
Place a dill pickle spear into each bun. Add a hot dog. Top with some of the pulled pork and some of the coleslaw.