I think my sister is a victim of abuse. Any advice?

I (23F) am extremely concerned for my sister (32F), who has been married to her husband (32M) for 7 years, but they have been together since they were both 16.

He comes from a family that seems nice on the outside but is incredibly toxic once you look past their plush lifestyle. For example, they constantly call each other names, mock each other for past mistakes, scream at each other for petty reasons, and I just found out that the women in the family often have to pull the men apart because they start physically fighting with intent to harm one another. Apparently, my sister's husband has used his family to hurt her. They broke up briefly in college, and my sister slept with someone else during the breakup. His family often mocks or shames her for this. On top of this, he will scream at her for embarrassing him and call her names in their home. They have young children, and he never helps because he is too busy with work. She once told me that he would not hold his baby to let her shower because the baby would cry. He talked her into having sex with him right after the birth of her first child because he got a doctor to agree that they only needed to wait two weeks. He prevents her from going to church because he is scared the kids will get sick at Sunday School. She's not allowed to spend money on herself or others. He forces her to work even though he makes 6 figures; she wants to be a stay-at-home mom, and he won't allow her to pay for daycare (she has to beg the grandparents to watch her children).

Those are a few things that come to mind, and I am genuinely so worried. Now, she is becoming someone I do not recognize. She is becoming so nasty and almost impossible to talk to without her ridiculing me or talking horribly about someone who offended her (it is very easy to offend her now).

I just do not know what to do. I want to be there for her, but she is in such denial and is honestly a toxic person now. IDK, I am just worried about her safety and need to vent, and I would love advice from people who have a better understanding of this stuff than I do.