Preheat the broiler. In a large bowl, combine the breadcrumbs with 1/3 cup water. In a large skillet, cook the bacon over medium heat. Transfer to a plate; pour all but 2 tsp. fat into a bowl. Add the onion to the skillet and cook over medium heat until softened, about 5 minutes. Stir in three-quarters of the garlic, the chiles and 2 tbsp. water, scraping up any browned bits; add to the breadcrumbs and let cool slightly.
Add the chicken, bacon and 1/4 cup cilantro to the breadcrumb mixture; season with salt and pepper. Form the mixture into 32 meatballs. Broil the meatballs, turning once, until just cooked through, about 12 minutes.
Meanwhile, in a large skillet, heat the reserved bacon fat over medium-high heat. Add the corn and cook undisturbed until it begins to brown, about 5 minutes. Stir in the cabbage and remaining garlic and cook, stirring, until the cabbage just begins to wilt, about 3 minutes. Stir in the remaining 1/4 cup cilantro; season with salt and pepper. Serve the meatballs in the tortillas with the cabbage slaw.