I hope i am in the right forum to post this.

I have a conundrum. I have been with my significant other for a few years (2 1/2). I met him while he was divorcing his spouse. ( I know bad mistake.) I found out later that she was diagnosed with Bipolar and had several hospital stays long term. Fast forward today and his divorce is has no end in sight. He is on his 2nd psych eval with her and still can't get her to make it through the tests. She has turned the kids on him and me (which i expected). We have a county court system that will not recognize the mental illnesses so they will not help them. GAL is no help and thinks she will get over it in time. There are no local attorneys that understand what they are witnessing in the evidence he gives them (texts, emails, voice messages) and just tell him "well you know she is crazy". I say illness plural btw because the first doctor believed she may also have BPD, HPD, NPD and paranoid personality. It is absolutely impossible to consider any form of co-parenting no matter how hard he tries at this point. She intentionally sabotages all efforts. His estate is being drained because she won't stop bringing up false allegations in court and she has an attorney that preys on the weakness of unstable individuals so he has run up fees in excess of $250,000. She is determined to burn the house down (figuratively speaking). He left her before we met but she thinks we had been dating for 10 years and that we have a child (just strange to even understand that one). It seems when her delusions become her reality she sets off on a course to use the legal system to chase down her false accusations to try to prove them correct with no avail. It is costing the children's inheritance. I do my best to ignore most of the daily drama but I feel so helpless. I caught my partner crying in the bathroom yesterday. Sometimes I almost feel like leaving him because it is just to much to watch. He is abused by the ex, kids and courts and he just sits back and cries. His kids have also been to psych docs since the age of 5 and 3 and have many issues. His oldest looks down on poor people and thinks the less fortunate are worthless and disgusting. This is a major problem for me as I came from a less fortunate background growing up and this makes me never want to have nothing to do with her (i don't see his kids as mom won't let them around me). I do not see a future for me and his children due to their mother and how they have been raised.

Here is my question:

Could it be possible that this is all just caused by a person devastated by the loss of her husband and going through a divorce? Is it possible it would stop after the divorce? Or would the illnesses themselves make it impossible to consider that "one day" maybe she will accept that he could no longer live with her and had to divorce her. Is there any way to manage this type of person that would stop this behavior? The children are suffering. She is alienating them ever so stealth like. My partner is suffering. The only one that is immune to the pain is her. Can i do anything to help my partner stop this or survive this torture he is subjected to daily.
Thanks so much for listening