Suggest Treatment For Forgetfulness, Tremors In The Body And Constipation

Question : My father married a woman from Guyana 40 years younger than him. I know daa. For the past 3 years he has been to a Gastro, Internist, Family Doc & other specialists. 3 years ago his stomach started cramping intermittently, than he was constipated all the time or had diarrhea and the doctor said he had a "twisted colon". Then he started shaking once in awhile and confused occasionally. Now he is shaking all the time and dz w/Parkinson's. Before he dies, I am trying to figure out what she is poisoning him with. My best friend in my previous state was from Guyana and she said "there are 2 kind of women from Guyana. There is me and than there are the women who sneak in this country and become aids to the elderly who die much too soon. Usually, those women marry a man 30+ years older than them and their husbands die from multiple dz" but it is actually a slow painful death from herbs or plants". He never had a tox screen for plants or herbs. Can you please tell me what herbs and plants when ingested affect the digestive system, then the mind and then slow walking and finally shakes? Thank you. This is private and confidential so please do not repeat this to anyone just in case he does have 6 different healthcare conditions & diseases.
Of course throwing up also. His health has been slowly deteriorating since getting married about 5 years. Before getting married he was vibrant and drove all over the place. He worked in one on the top 5 accounting firms.
PS Over the past 3 to 5 years, his mobility has decreased dramatically & his mental well-being is becoming slower, more confused & forgetful. He is always in gastric pain and cannot commit to yes to any event (esp his brother's house which he loves going to), it depends on how he feels when he wakes up. Multiple neighbors have confirmed a boyfriend coming over after midnight (she sleeps upstairs in the bed my mother slept in for 50 years and Pop sleeps downstairs). He got married so he wouldn't sleep alone. All the neighbors are coming up to me and asking me "what is that woman doing to your father'? Before his mind became too slow, He paid for her mother's kidney dialysis for 3 months, fixed her kids' house which did not have running water or any plumbing and paid for her mother's funeral as well as many gifts. Her kids have not come to visit and she hasn't seen them in 20 years. I believe she is a sociopath. I have to narrow down some of the poisonous plants, pesticides, coils, etc to add to tox screen BEFORE he dies. I am rushing my surgery & putting in a stimulator on the bottom of the spine so I can get back to work quick and do a sweep of his house when she is not home. Need to know what to look for. Please help. He is very fragile and we all know when a man is getting some, he does not use the correct brain upstairs. She was an Aide to the elderly but barely speaks to him but shops a lot. He said he was marrying her so he would have someone to take care of him and not being along. IMPORTANT - newest symptom is he is sleeping too many hours and when I hug him, he is very stiff & involuntarily his arms move inward (like a pt who needs Baclofen).
He will not tell us the meds he is on. One is for the shakes but this seems to be a slow poisoning. Worked on 2 cases and they are very similar. The slow introduction of a toxin or herbal toxin my father's condition is following. I just need to research some of the plants or herbs from Guyana for Medical Examiner or doctor now before it is too late. I will be able to figure out which one she is using. Initially, I wanted to be a medical examiner but I had to raise my mother's three kids so my life was put on hold. Now I am getting SAFE certified. I am a RN who is very competent and would eventually be a researcher. thank u. Please give me some ideas. Thank u very any ideas.