This would be a good issue to raise on the Questions, something such as, "How to cope? Since dad's diagnosis, surgery and treatment he has changed completely to become very angry and nasty." People will share their experiences and may have some coping strategies.
Cancer fighters have a difficult burden to bear - dealing with both the psychological, financial and physical challenges of dealing with cancer. Plus dealing with work and how to be around family. It sounds like your dad is going through a really hard time. Does he attend any support groups? Does he have support at home? And of course, all this is tough on you. Cancer doesn't happen just to the person diagnosed, it impacts family and friends, too. If/when you are ready, please reach out to the network. I think you'll find that many have been in your shoes and will want to help. Thank you for being here.