555: That is completely wrong. Wow. I don’t even know where to begin.
Have you never heard of the concept of Aseh Docheh Lo Sa’aseh? It’s kinda an important rule in lots of things that we do. You should look at the beginning of Yevamos.
Also, fasting on Shabbos isn’t a Bittul Asei. Oneg is only D’rabannan. So it’s a Bittul Asei D’rabannan.