I agree with the others - it appears to be that your finance has depression going on and is just plain afraid of doing anything that may stress his heart. I am surprised his Dr. did not suggest a cardiac rehabilitation program for him. Cardiac rehabilitation services are designed to help a person to recover faster and to return to a full and productive life.
Having a heart attack can be very frightening and traumatic, and afterwards
it is common to have feelings of anxiety. For many people, the emotional
stresses can cause them to feel depressed and tearful for the first few weeks
after returning home from hospital. Your fiance has had 2 attacks now so I suspect he is very frightened.
If feelings of depression persist, let your fiance's GP know about it. The Dr. won't be able to discuss your fiance's problems with you but at least you have let him know.
Most of al let him know you are there for him but don't enable him to be a cardiac cripple.