Contact the social worker at the hospital/center where your father is being treated and find out what services he qualifies for. I know in NYC cancer patients can get free cleaning services, meals delivered, etc. Also see if you can get him to see a therapist that specializes in treating cancer patients. It sounds like your dad is depressed. Also find a support group and/or therapist for yourself. You need to take care of yourself.
Being a caregiver is one of the hardest jobs in the world. Do you have any family or relatives who can help support you and your father. Someone who can come and stay with him so you can get away for a well deserved long week-end if not more time.
Best of luck.