My concern is he has moments of being civil to outright rude to me. If I bring it to his attention he says he does not like to be challenged. I never know when he is going to go off on me. My question is there any benefit to documenting these episodes? Any other suggestions would be appreciated. His provider, Veterans Admin. already said they would not do an MRI
Do these outbursts come late in the afternoon? If so, it may be sundowning. Chemo for bladder cancer is fairly invasive since it is directly put into the bladder. Both my parents had it. Dad in his 70s, Mom at 80. There was no after effects. As long as the cancer hasn't broken thru the wall of the bladder and spread, its curable. Has Dad always been this way or only since the Chemo.
"He does not like to be challenged" What do you do that makes him feel challenged? Remember, you are the child. At 95 I wouldn't push him to do what he doesn't want to. Pick your battles.
As far as challenging him, it can be something as simple as disagreeing with him about a topic of discussion, my choice of making a change to surroundings ie move a chair, a plant..doesn't matter. I am concerned that if this is Dementia/Alzeimer's approaching which is best to worry about.
https://www.agingcare.com/products/being-mortal-medicine-and-what-matters-in-the-end-433866.htm
or AgingCare has this article
https://www.agingcare.com/articles/an-end-of-life-conversation-led-by-gawandes-questions-205721.htm
If the cancer is contained to the bladder, there may not be any pain. The only way my parents were aware of a problem was when they had blood in their urine. Mom had the cancer in the tube going to a kidney. That and the kidney were removed. After a scope a few months later, lesions were found in the bladder itself and she started Chemo. If caught early it very curable. Then a scope every 3 months, then 6, then a year.