For the sake of exploring this, why don't we conduct a thought experiment and remove birth sex, current sex, and gender from this story. Just to consider how much of a factor these things really are.
A person in a wealthy nation leaves their partner and fellow parent to their children for their domestic servant. This servant is a foreign national who is brought to the wealthy nation at great expense. They marry. After about twenty years, their marriage begins to break down due to two issues. The younger partner possibly has been frequenting bars and cheating on their spouse. The younger partner also has been spending increasing amounts of time working for herself. When these issues come to a boiling point, their relationship comes to an explosive end.
We could point out a lot of possible dynamics at play here. To start with, lets look at our older partner. He left his wife for their much younger servant. Interestingly, he seems to have a habit of leaving women once their age and the duration of their marriage hits a certain point. We could very easily say he's simply the kind of man who cannot maintain a relationship with a woman past middle age. Some men require a young-looking woman by their side to feed their ego. Or maybe what he really wanted was somebody to serve him and dote on him, which is why he divorced the first wife and married her in the first place. It would make sense. She started as his maid, and apparently her new full time job was a huge stress on him. Or maybe none of that is true. Maybe his first wife was simply bad for him, and maybe his current anger (though the violence is unjustifiable) is a legitimate response to his wife cheating.
Look at our younger partner. She married a 48 year-old man when she was 32, knowing that he divorced his older wife to get to her. It's possible she didn't really think through the realities of marrying a man twenty years older. He would be slowing down sexually and physically at an age where she might want to still be going out on the town, and she didn't consider the consequences of her decision. It's also possible she knew that and didn't care, that the reason which pushed her over the edge and convinced her to marry him was the lure of a stable life in a wealthy nation. Regardless, she apparently did frequent bars and nightclubs and sometimes cavorted with other men. Whatever the case, she had clear disrespect and disregard for his feelings. Or maybe she had to act this way. Maybe he was a controlling man who loved her when she was his submissive maid but was filled with rage when she began to become independent. Maybe finding comfort in the arms of other men in secret was her only way out.
None of that even touches the trans issue. Yeah, it's all blind speculation. Just trying to illuminate the range of possibilities.
I'm not saying either one is sinner or saint. I honestly just see this as a relationship which is profoundly broken on many levels, independent of her trans issues. And this is going to be one of those brutal, messy divorces, something cis people are equally prone to. Some people just want revenge when their serious relationships end, up to and including any kind of public humiliation or legal extortion they can inflict. I just see his trans comments as a petty attack on her, and his hiring of a lawyer as a spiteful attempt to exact vengeance. I don't think trans issues are the key points here.
