Korean-Chinese sweet and sour sauce (for tang soo yook)

We ordered chicken tang soo yook from a restaurant far from our neighborhood. When we got home, we discovered to our dismay that the restaurant forgot to include the sauce. We made our own sauce following this Maangchi recipe: https://www.maangchi.com/recipe/tangsuyuk. Our modifications: we omitted the wood ear mushrooms and cucumber. We used ½ yellow bell pepper, 1 small carrot, 1 small onion, ½ of a Fuji apple, and about ¼ cup drained pineapple chunks from a can. For the potato starch, we used ¼ cup mixed with ¼ cup room temp water; we unceremoniously dumped mixture into the pan, which led to lumps; the next time we will carefully drizzle it into the pan, using a whisk. We found the recipe lacking in acid and sweetness, so we ended up doubling the vinegar to a total of 6 Tbsp (we used a mix of white vinegar and apple cider vinegar) for proper tanginess. In addition to the sugar and salt already called for in the recipe, we added 1 ½ Tbsp white sugar and ½ tsp soy sauce (the latter mainly was for color). After such tinkering, the sauce turned out pretty close to authentic. (Oct. 2020)

Note: We reheated the fried batter-dipped chicken in a preheated 425 oven for 9 mins.