I have a father like that. Hard headed. Try to be there for your mum and the rest of the family. The cancer will eventually make him give in. Until then take care of each other. It sounds like it wont be long before he will not have a choice but to ask for help. It will happen believe me. For now your family needs to keep it together the best they can for all of you. That way your all better prepared when it's time to deal with dad. If you can keep doing normal everyday life things that  will help you all pass the time. It will all fall in to place when he's ready or the cancer makes him ready. One or the other will happen and then you will be able to connect with him. I will say a prayer for your family. Take care and try to stay strong for all of you............Adam W.