I'm sorry to hear about your sad situation.
You should not feel guilty about hitting your dad. You did the only thing you could to try and stop the situation, you have my respect, not because of the 'hit', but because you acted and because you care.
I feel that you have taken on a responsibility that is not yours to carry. Of course all of us care about our parents, but you must understand that they are adults who can take care of themselves and sort out their own lives.
The role of a parent is to nurture a child and to gift that child with the skills to leave home and become independent and start their own life.
It is time for you to find a way to leave home, there are many people who rent out rooms, perhaps this is an option you should consider and one that should be affordable.
If you are being or have been emotionally manipulated (ie your parents have made you feel that you are responsible for them and that you owe them something), then it's time for you to break the spell.
You are your own man now, an adult, and so are they, you must do what it takes for you to survive and be a content person, and remaining at home is simply no longer a choice, I hope you find the strength to leave.
I think it's easier said than done.