My mother had a heart attack... previous to this, she wasn't crazy unhealthy, it was actually caused by other underlying health issues... but even so, she went through a period of time where she was really uncooperative about food, medication, exercise... pretty much anything she was 'supposed' to be doing. She was resentful of 'having' to do it, because she felt it was 'unfair' that she was in this situation.
It was a real problem in our household for a while, not just because we were worried about her, but because everything was so tense all the time. Eventually, I snapped.
I was picking up dirty dishes from beside her bed, and found the binder of info from the Dr. shoved under her bed and covered in dust. It hadn't moved or been touched in a week or two. We had all been working so hard to help her get better, and she hadn't even so much as read any of the info the Dr's had given her... I got frustrated. I told her if she wanted to fucking die because she wanted to act like a child and do the exact opposite from everything she had raised me to believe (she's usually very level-headed and believes strongly in common sense), there was nothing I could do about it and I wouldn't stick around to watch her die. I kind of wish I'd stopped there... but I was mad. I continued on to say that if she DID die without having followed the doctors orders, I wouldn't have anything to do with her funeral or memory. I'd disown her after death. She locked herself in her room and cried for like three days... I felt like the worst daughter in the world. It was a cruel thing to say, and ends don't justify the means. I wish I could have done something differently.
But....when she eventually came out, she finally opened up about how overwhelmed and persecuted she felt, and apologized for making everything so difficult for our family. She's doing much better now... but the biggest thing was to realize that she's not a victim, and that acting like everything is a big punishment was only making everything worse.
The only thing that I can realistically see you helping him with is getting him 'on board' with his own recovery. He needs to realize that none of this is for your benefit, and that HE needs to actually do something for HIMSELF. Recovering from and preventing future heart attacks isn't something that other people can do for you... unless he can snap out of this ignorant, whiney attitude of "but I don't like it", I don't see how you'll be able to influence his future health all by yourself.
I hate to say it, but your father needs a serious reality check, and needs to 'suck it up' and stop his complaining. His childishness is going to get him killed. I don't know how you communicate that to a grown adult who should know better. If he respects the Dr's at all (which I'm guessing he probably doesn't much) perhaps one of them should give him a talking to, if he wont listen to you.