My father is having an affair while still recovering from multiple organ failure. What can I do?

My father suffered from multiple organ failure last year. He was in the two hospitals and 3 nursing and rehab facilities for a total of five months in 2016.
He now is recovering at home. It will take some to qualify for a heart surgery because he is still in the healing process.

He started sneaking out of the house to be with his girlfriend. Ever since he started going out with her again, his health started going down. He ended up with pneumonia and breathing problems and is currently in the hospital for treatment.

I managed to block the girlfriends number on his cell phone, but I will obviously need to confront him about it almost immediately after he comes home. He also wants to renew him driver's license. I have a feeling that he and his girlfriend are planning something probably around his birthday time because he has been wanting to renew his license for a while.

I know that as his caregiver, he is not capable of driving because he is still healing from multiple organ failure. He still needs to work on qualifying for a heart surgery to improve his problem with his aortic valve. He tends to be sleepy anytime of day especially after meals. He is physically and cognitively slower. He is able to make decisions, however not prudent ones. I think he still needs to improve his red blood cell count. I know he lost weight because prior to being hospitalized for pneumonia, he started losing his appetite. He barely ate anything in the hospital. He had lung swelling because of fluid around his heart had gotten into his lungs. They gave him diuretics to drain out the fluid which they did successfully. However, he is still sensitive and susceptible to having set backs.

How can I convince him that he is not able to drive and should not do so because I know he wants to visit his girlfriend. He has also been manipulated by her to take out money from his savings. He has taken out over $10,000 of his savings/retirement money to give to her in a four month period. How can I make him understand that she has only been using and manipulating him for money by making him feel good. She gives him all sorts of ideas and acts like she is the only one who understands him. How can I make him understand that she is only using him before his retirement money runs out. He doesn't have enough in his retirement and needs to pay for medical bills. Since he does not have enough for retirement, he may not have enough to pay for medical bills and may not be able to have enough for long term care. He is 79 years old. He is going to be 80 on February 13, 2017. He is much closer to his girlfriend than he is to me and my mom. My family fought to keep him alive while he was in the hospital and miraculously did well until he started sneaking out with his girlfriend again. He is depressed, but does not except help. He never admits when he needs help. Even when he had difficulty breathing, I had to call 911 based on his behavior because he never asks for help. How can I get help in handling this situation? Is there legal help for this kind of situation? Is there a way to stop his girlfriend from manipulating my dad who is still recovering from multiple organ failure? Is there some expert I can ask for advice in talking to my dad about his wrong doings and his girlfriends actions as well? Is there any professionals I can talk to? We do not have money to higher a lawyer or hire an investigator.

I also need help in convincing my parents to agree to have someone look after them in case one of them has a medical emergency because I cannot be in two places at the same time which has already happened. I do not know what to do. I am clueless. Any advice would help.