Dad refusing to take care of himself. He is frustrated and maybe depressed.

My dad has uncontrolled diabeties, 185 - 300 with 2 injections daily of longlasting insulin and 1 injection daily of fast acting. My mom passed over 5 years ago, my brother who lived with them passed in october. I think my dad is depressed and lonley. I take him to every doc apointment and try to keep things undercontrol. He plays dumb about carbohydrates and is out eating his insulin. He does not drink. He likes his sweets, icecream. His endocrin doc told him today he needs another of the fast acting insulin injections daily. He is having a melt down. refusing to take his blood sugar readings and says he is too busy to inject himself 4 times a day. She said he can take 3 combined injections but he has to eat within 10 mins of the injection. He is refusing. I said this is your disease and you need to do whats best. No one can do it for you. He started to have a meltdown and dropped the F bomb for the rest of the time I was with him quite a bit. I know he is frustrated but what can I do next? I've discussed him seeing a psycotherapist for his depression he says no. I've tried to have him move into a senior high rise so he will be more social he says no. He does go to a senior center twice a week and does have some friends but he exercises very little. I don't think he is showering often. what can I do?