that sounds fucking horrible.. but praying or any repeated thoughts can actually help with anxiety so there is that. when i was little i used to pray the rosary in order to calm my nerves so i could go to sleep.. even though i didnt believe in what i was doing, it relaxed me.
but yeah, i feel for you. my dad was like that and still is, most older people are quite stuck in their ways so i doubt they will change much. deep down i think everyone has the ability to have compassion and look beyond their own believes to meet a common ground, so maybe try to come at them in a sincere way and avoid talks about religion. if it doesnt help you might want to talk to a teacher or doctor to seek help from an outside source.