Cheesy Mini Meatball Skillet Dip

Name: Cheesy Mini Meatball Skillet Dip
Ingredients: 12 oz. hot Italian sausage, casings discarded, shaped into ½” balls; 1 small red onion, finely chopped; 1 jalapeño, finely chopped; 3 cloves garlic, finely chopped; 1/2 tsp. kosher salt; 1/2 tsp. freshly ground black pepper; 1 c. BBQ sauce; 1 (8-oz.) block cream cheese, cubed; 3/4 c. freshly shredded American cheese; 3/4 c. freshly shredded cheddar; 1/4 c. pickled red onions, finely chopped, plus more for topping; 1/4 c. whole milk; 1 scallion, thinly sliced, for topping; Tortilla chips, for serving