my sister is contemplating filing for divorce against my brother in law who has lost his fucking mind lately and been diagnosed with paranoid schizophrenia.
he believes she is trying to kill him, he tells her every day that he doesn't love her and he thinks she's a horrible person. he believes my family is part of a satanic cult/meth making ring that's trying to impregnate his daughter.
he believes the hospital he was court ordered into is owned by my parents and that the doctors were trying to kill him.
It's more creative than any sci-fi movie I've ever seen. The sad thing is at one point he was a normal guy and a great husband/father.

Anyway... is anyone aware of a good divorce lawyer with experience with mental illness and farm finances in eastern Iowa.

Where in eastern Iowa specifically?  Attorney travel time/expenses are not cheap.

Have her get a voice recorder they are pretty cheep and keep records of what he says or him saying it. It will help threw the whole process then it's not a he said she said situation. Otherwise I have lawyer zero experience

Non-lawyer advice: You used the past tense in reference to him being in a mental health facility. If he isn't currently involuntarily institutionalized, you should get your sister and the kids out of there, now, with a LEO present. Then get the lawyer.

I had a friend that had paranoid schizophrenia onset in his mid-20s. He murdered a family member.

I think all lawyers have a mental illness.

Or if she loves him she could also stay with him and try to get
Him the help he needs.

I listened to the mother of a kid who murdered his high school foot ball coach a few years back talk last week.  Get your family far away because sooner or later satan is gonna need a bullet.  Iowa mental health doesn't seem to be in too healthy of a state and you need to keep her and family safe right now.

Here is a little light reading on mental health committals in Iowa.

https://www.legis.iowa.gov/DOCS/Central/Guides/involuntary.pdf  

And another fubar decision by the US Supremes.  Them guys can screw up a wet dream.
https://en.wikipedia.org/wiki/O'Connor_v._Donaldson

Good luck for your sister.  I like the idea of recording all conversations.  

kwg

He went to talk to a shrink at one point and based on the things he said the shrink got a court order to institutionalize him for a few days. During this time he was diagnosed with paranoid schizophrenia. There was a court order (he did not know at the time) but he went voluntarily.
Would this show up on a NICS check if he attempted to obtain a gun? Does this make him a prohibited person?
As of right now I have my sisters AR15 and .22 rascal in my safe and his mother has his fathers old shotgun at her house.

Don't view 'lack of gun' as 'safe'.  Remember that most murders are not related to guns, it's just one tool.

Here is Iowa's online case search: https://www.iowacourts.state.ia.us/ESAWebApp/TrialSimpFrame
I do now know if mental health proceedings will show up there for you, though.