My mother died of a heart attack at 55, my husband's mother at 47 so we understand your concerns. I am glad your dad is recovering! A couple of quick pieces of advice:
Check out www.youvegotsupper.com - if you subscribe they will email you a list of recipes each week and they just added a feature where they list at least one heart healthy recipe per week. or you can just search their website for some heart healthy recipes.
Mrs. Dash...comes in a lot of varieties now and tastes great on everything! Chicken, red meat (lean of course), pasta, etc. We skip added salt altogether as there is more than enough in food already.
Skip processed foods - most frozen foods, broths, soups, luncheon meat, hot dogs, etc.
Find the DASH diet online - will give you great ideas for how he should eat.
I just got a free Light & Easy recipe book from the American Heart Association courtesy of Merck. Looks like it has some yummy recipes. Sorry I don't have the link anymore but a Google search should bring it up.
I would say you are going to have to start bypassing salt, sugar and butter but there are some good alternatives. As for sugar, I know there is Splenda and Truvia (sp?) which are supposed to come from real sugar. Don't know about chemical additives. There are good butter alternatives too but yes, I think they have chemicals. Personally, I use olive oil 99% of the time and when necessary for butter, go ahead with the real thing (unsalted) but just in moderation.
Good luck!!!