On the contrary. The first two things are nothing with this. If he is really a good mother, like a loving mother in a TV series, as you said, don't believe in TV series. We live in reality, TV series is a transformed life, an idealized thing, and it is immature to cover real life with TV series. I like to eat large portions and small portions. I can be careless or coquetry at home. Now I'm starting to suffer. Your home may be in the countryside, where people's emotions are not as detailed as TV dramas.
The third thing is not easy to do, but it also happens for a reason. At least your father may be a bad person. It is also possible that your mother is a person with weak emotional awareness and sense of responsibility, which was not formed in one day and may change in her later life. Don't take it as a big deal, the sky will not fall.
The object of mother's infidelity is not her father-in-law, but the people in the same village. See if she has affected the normal life of the family and what is the main reason. If the third thing can be put down, the rest is not important.
But one thing, don't compare literary works with real life, then you will be fooled.