I am a primary caregiver to an 88-year-old man whom I have known before the onset of dementia. How do I deal with his delusions?

He was first a pilot in the Air Force for 20 years and then a private commercial jet for 30 years. A full life with 3 sons and now he deficates and plays with it and is destroying furniture and hurting himself. We want to keep him in his home of 60 years but he thinks people are coming in, stealing and his deceased wife of 15 years is in bed with him. I need help and the neurologist just prescribes numbing drugs. Please help me