Hola Amigos, great posts on the infamous KT sauce but I think you're making this more dificult than it is. I am a salsa fanatic and have a variety of salsas for different dishes and all serve a different purpose. The main idea behind a salsa is to provide a hightened taste experience of the main dish and not to overwhelm it.

Keep your salsas simple and "take it eeezy" as Nacho Libre would say. Oil, Manteca, and vinegar have no place in salsas in my opinion. Oil and manteca are for cooking meat/other dishes not salsas. Vinegar just ruins a salsa and changes the main dish mainly by over taking the flavor. Vinegar is very strong.

The vinegary taste in the KT salsa can also be achieved by using the small green tomatillos that are wrapped in thin husks. Give those a shot by either roasting them or boiling them just enough to cook the tomatillos half way. Try different times for the boiling cook time since this will also render different flavors.

BTW, there is a taste difference between the green tomatillos that are about 1/3 the size of a regular tomato and the tiny tomatillos that are about 1/8 the size of a regular tomato.
Although I can't provide a close suggestion to the highly guarded KT red sauce, I can tell you that I'm pretty sure the ingredients are simple and few. I do have a red sauce that we make for pozole and it's every bit as spicey as the KT sauce but it does not have the tangy citrus taste. I can taste cumin, garlic, chicken broth powder and chile poblano in the KT sauce though. Give that a try, you will need to play with the ingredient measurements though, "Measure twice, cut once" my shop teacher used to say. Arriba, Arriba, Andale, Andale!