Is my Father mentally ill or is he abusing my Mother?

In the early 70s my parents had marital problems. They were in their 20s, my mother was working at a bank and my father was just getting his career started as a business analyst. My father made the ultimatum that either my mother quit her job or they get a divorce. My mother chose their marriage. She gave birth to my sister a few years later, and then me 9 years after that. Everything was fine until my dad's company announced they were moving and laying off a good portion of their employees. My dad made the cut but decided to leave his job instead of move. My sister was in college and staying at home. I was in 8th grade. My father got another job as a contractor about 9 months later, but only worked for 5 months until they let him go.

After this my dad's personality changed. He became a lot more explosive, reclusive, lazy, and increasingly irresponsible with money. (As background, my father has always had trouble with his heart. He has had numerous strokes, two heart attacks, and a quintuple bypass.) My mother tried to talk to him about getting a new job, but he wouldnt talk to her. My mother always managed their bank accounts. When she stopped being able to do so, she gave them to my dad and told him to figure it out hoping that it would inspire him to find a new job. He cleared out their bank accounts, their retirement savings, took out extra mortgages on the house... Meanwhile, my mother had major surgery after major surgery. She has had spinal surgery, two knee replacements, shoulder surgery, gall bladder removal, etc etc. She became incapable of working and my father refused to get a job. He started to forget to pay bills. Utilities are repeatedly shut off. He stopped taking care of his health and started eating really unhealthy. He turned 65 and started get social security... he refused to let my mom have any spending power, canceled her credit cards, etc. He stopped taking care of his health and eats really unhealthily. He forces my mom to eat "crap" and she has no choice but to...

My father drove out into an intersection without looking in December on their way to a doctors appoint for my mom. My mother hurt her ankle and hit her head. She needed stiches. It was a month after this that my mother was diagnosed with extensive small cell cancer. She started chemo and is doing fairly well despite the grim outlook on the cancer. Only problem is that my father refused to buy nutritious meals for her. He tells her that he wants her to die. She started having to take insulin shots and he refuses to give them to her (she is deathly afraid of needles and incapable of giving them to herself). She cannot drive herself to her appointments because of arthritis and blurry vision. He is started to tell her that he wont drive her to her treatment or pay for her treatment copays. He set up their social security where only he has access to their checks. My mother has no money of her own anymore because my father took it to pay the bills. He is still horribly late on payments. Their air conditioning is about to get shut off from lack of payment. My father has lost numerous teeth from his bad diet and lack of hygiene. He doesnt talk to anyone and randomly goes off his heart and diabetes medication. He also tells my mom that their financial trouble is all her fault. He tells his family that it is all her fault too-- and they believe him! He told her that she needs to start financially contributing to her treatment, but he is already taking her checks!

My sister is working part-time at an animal shelter for low pay and I am in school out of state and working a job for low pay. What do I do? Is my father mentally ill or is he abusive? I am unsure if he even knows what is going on in his life anymore. I don't really know what to do...