Is there a medical aspect of project management?

The fact that your father fought during a war (is it the Biafran war?) raises the possibility of him having a Post-traumatic stress disorder (PTSD), a reaction to extraordinarily stress events. One of the many features of the disorder is excessive irritability, usually accompanied by drugs & alcohol abuse, which in turn worsens sufferers social, occupational and family functioning. The undue suspicion he has that your mother wants to kill him (after 33yrs of living together, and with many opportunities to kill him had she wished) is also rather strange. Why not persuade him to see a mental health practitioner for evaluation/assessment.