How to help my dad

We lost my mom 1 1/2 years ago. Dad is 87. He does well for 87, however, I don't think he takes his meds. as he should, he has no computer, he wears no hearing aid. HIs activity level has decreased He has an enlarged heart, has had. He stays winded, I have managed to get him to doctor once since she passed. He tells me he will deal with it, but doesn't. I got him a lawnmower in spring that maybe was used 3 times. He doesn't eat much, lost 20 or more pounds. I am an only, and I try to help as much as possible, we talk everyday. He lives where he did for over 50 years. He will not move. I think moving would bring him down more. I know he has depression and if I can get him to doctor, I will discuss this. We end up in more disagreements, as he still thinks he is boss and I am 5 years old. I love him dearly, I try to make my ideas sound like his. I am worried about him. I need advise.