Suggest Precautions To Be Taken For A Low Heart Functioning Rate?

Unfortunately, I don t have all details. My daughter has fallen in love with a man that has had heart problems since in his 30 s. He had a valve replaced and pacemaker put in .this was in the late 1980 s. In the last year, he had to have open heart surgery, a second time to replace valve. They said with new technology it won t have to be done again. Since that surgery, his state of health has slowly but regularly declined. He can t walk from one end of house to other without breathing hard, looking stressed. According to him, cardiologist says your fine. But you only have 25 % heart function left. They did not put him on 02, told him to deep pulmonologist, who gave him an inhaler that hasn t helped much. I have a medical background, but he is not proactive. He eats prepared and fried foods daily, and refuses to Change eating habits even though my daughter and I live with him and we eat a mainly plant based diet. I realize there is limited medical information here, I m trying to find more. But I feel my daughter does not realize the seriousness of this. Any tips, for a concerned family member? Even for him? I m continuously trying to lead him towards a healthier life styl,with much resistance.