Season the pork with salt and pepper. Place in a braising pan and add the onion, vinegar, and BBQ sauce. Toss well. Braise for 3 hours, covered, until fork tender. Remove meat with a slotted spoon and "pull" with forks until shredded. Add braising liquid, to taste. Cool.
For the slaw: Mix the mayonnaise, vinegar, sugar, celery salt, garlic salt, and pepper in a large bowl. Add the vegetables and mix thoroughly. Let sit 10 to 15 minutes before serving.
For the egg rolls: In large saucepan, heat the vegetable oil to 350 degrees F. Add enough oil to keep the egg rolls from touching the bottom of the pan.
In a shallow bowl, beat the eggs and milk together and set aside.
With the corner of the wrappers facing you, place approximately 1/12th of the pulled pork on each wrapper. Place a dollop of coleslaw on top. Fold the corner over the filling, and then fold the outside corners in, making a roll a 4 to 5-inches wide. Roll firmly, being careful to not tear wrapper, and seal the final end with egg wash.
Dredge the roll in egg wash, allow excess to drain off, and submerge the roll in the hot oil. Fry until golden brown. Drain on paper towels and cut on an angle, if desired.