Anger & estrangements with relatives who are battling cancer

Hello - this is my 1st post.  My father was diagnosed with Stage 3 lung cancer, probably about a year ago, after a couple of missed x-rays.  Has anyone else been through this?  He is currently undergoing his 2nd round of chemo, a triple dose this time, and is finding side effects a lot harder on this round.  Having always struggled with the relationship with my Dad - he was quite a controlling and bullying man & I have spent my entire life trying to please him, he is currently undergoing an extremely angry phase.  Every convo we have is about how we are living in a 3rd World country, the NHS have taken years off of his life.  He is an ex-smoker and lived with emphysema for 20 years prior to being diagnosed, so has done remarkably well - he will be 76 this May!  Because I am daring to actually not be brow-beaten down and am trying to remind him of the positives within the NHS, he has taken it that I am disrespectful and has disowned me - he will only talk to me basically if I grovel to him and apologise.  He probably only has this year left, realistically - I believe he needs to direct this anger out to a therapist rather than to myself and my put-upon stepmother, but do not think he would ever do this - any thoughts/suggestions anyone may have or views from anyone that may have experienced similar would be greatly appreciated.  May I also add that I was in mainly abusive relationships prior to my current one, probably due to the relationship that I had with my father, and met my partner in life and went on to have a miracle baby boy at the age of 45 - he is now 5 years old and is my father's only biological grandchild.  He hasn't had too much time with Lucas, due to location (we live an hour & a half apart) and his age/health meaning that he doesn't travel now, but this estrangement would also mean him not seeing this amazing little boy either.  Thank you for listening and wish you all the best in your difficult journeys...…. xx