Sorry about your dad.
Heart attacks kill heart muscle.
Without viable muscle the heart cannot pump properly or efficiently. You father may not improve significantly depending on the actual amount of heart muscle damage. However, If the muscle is just stunned as opposed to dead he could get better with proper exercise, diet, and medication. Also I would wonder why he is not a candidate for bypass surgery if he is having angina. I would urge you to go within the military system to get a second opinion and even though it may cost a lot, that you would have to pay personally, if there is any way you can I would urge a second opinion at a reputable private facility or cardiologist group like the Cleveland Clinic, or Johns Hoskins, etc.