In a medium bowl, combine fish and 2 tbsp. each of lime and lemon juice. Cover and refrigerate at least 3 hours and up to 6, stirring occasionally.
Meanwhile, mix olive oil, oregano (rubbed between your palms first if the flecks are large), and pickled jalapeño juice in a large bowl.
Drain fish in a colander, discarding juices, and add to olive-oil mixture. Toss to coat.
Add pickled jalapeños, onion, tomatoes, cucumber, olives, cheese, serrano, and cilantro. Peel avocado, cut into 1/2-in. cubes, and toss gently with remaining 1 tbsp. lemon juice; add to bowl and toss ceviche gently and thoroughly. Season to taste with salt and remaining 1 tbsp. lime juice. Serve with tortilla chips and hot chile sauce.
Note: Nutritional analysis is per serving.