If your father is asymptomatic with his level of daily activity, on good medications for the heart, then there is no role for coronary interventions; a stress test
would not be useful either. Results from a huge recent trial called COURAGE indicate that stable patients with chronic stable coronary artery
disease can do really well with medications.
To the second question, there is no role to do a stress test now after the recent diagnostic angiogram, it is like trying to climb a tree by sliding down.
Hope this helps
Mayo Clinic Rochester