Anyone knows of any tingkat service which allows us to choose only 3 times a week instead of the usual 5 days?

Maybe you consider FitThree? It's not exactly tingkat meals but it is packaged in recyclable containers and the meals are catered to be healthy and especially for those who are on a diet or working out. They offer a 3 day meal plan as well as a 5 day one. I've actually tried some of the meals (swiped them off a friend who orders regularly from FitThree) and they are pretty good. https://www.fitthree.com/howitworks