My mother is Jewish and I was raised Jewish. My dad converted in the reform tradition and I know what that means. Recently he's become ill, I am scared of what that means. I am incredibly close with both of my parents. They have been married just over 45 years and I am struggling to come to grips with their mortality as they age. How do I daven for a non-Jew in times like these. To put it into context, my father is seeing an oncologist tomorrow and I have a good idea of the outcome. Any wisdom or guidance would be helpful.
The standard approach is to Daven for him as (name) ben (father's name) based on the Maharshal, although there are other customs.
See also Yechaveh Da'as 6:60 for more on praying for a non-Jewish parent.
Wishing him a speedy refuah sheleimah and may you all share many more years of excellent health.