YTA.

I'm not even looking at this thing from a parent's point of view at this point but from a sister's viewpoint.

The most dangerous time in a woman's life is when she is getting divorced, whether there has been abuse or not. A little bit of flexibility would not have killed you. Are you not concerned about your sister? When asked why you had to take a shower right then you said - "I had things to do and needed a shower" ok and your sister is about to go through something really scary so maybe the errands can wait a little bit? No one asked you to hold off on a shower because your husband wanted to play video games, and your husband was helping your sister with a serious situation. A child will not die from being verbally scolded, by a woman can is she isn't careful when leaving a spouse. And you kicked her out of your home because your 2-year-old cried after getting scolded by his dad who had already asked him to stop, and who was trying to comfort his son and apologize to him for getting angry? YTA because you weren't being a good sister OP and while being a mom comes first, your reaction was ridiculous and unwarranted.