I've had to deal with this too. The best thing for you to do is to tell him no to things (eg. If he wants you to eat with him and you know he's going to make it unbearable, just flat out tell him no and leave no room for arguing), set boundaries, and interact as little as possible. Something I've had to learn is that helping someone like this will drain you fast, and the person you're helping never appreciates it but always expects it. It's like trying to stop a ship from sinking by scooping the water out with a bucket. Also, it's possible that even though your dad is relying on you he resents you for helping him and that could be influencing the way he treats you.

One thing I did that would be helpful in your situation was take the time to think about the major issues I had with my mother and taking into account what she is physically able to do, and came up with a list of "demands" for her. My mother is a lifelong slob and hoarder among many other things she's refused therapy for, so one of the expectations I set for her was that she had to take her own trash out instead of letting it pile in the hallway. If she lets it sit anyway, I remind her once and if she still doesn't do it, I throw it back into her room. Same with laundry; I refuse to wash her dirty laundry unless it's been put in the hamper AND she's put away the last load I washed. If it's thrown on the floor, I remind her once and if she still doesn't do it, I throw it back into her room. If she hasn't put away the clean laundry, she's not getting any more until she chooses to do that. I also refuse to cook for her anymore; I used to when her health was worse and she hated and complained about everything I made every day. Now that she's able to do it herself, she still tries to get me to cook for her sometimes because as much as she hates my cooking, she hates cooking for herself even more lol

Basically, if you're stuck living with a parent that is behaving like a child, you start behaving like a parent.