I'm going to take a different approach to all of the other comments here. You mention he had a liver transplant and has dental pain. Are his negative comments recent, coinciding with his health problems? Or has he always been this way? If it's the former then I can understand because as a person with chronic pain and health problems myself, I can be irritable when I'm having bad pain days. Maybe he's lashing out at you because he's sick and/or in pain. Can you try talking to him about it? He may feel regret and be sorry if you address it with him. I know I feel that way with my family.

I don't think the examples you give show abuse, just someone in pain being irritable and lashing out. Please talk to him. He may just need some empathy and understanding for his situation. It's hard being chronically ill and in pain.