Everyone has a difficult experience, and your experience is definitely not the worst, so I hope you will not be too pessimistic and full of resentment. As for dad, you should tell him calmly when he doesn't drink and is in a good mood, and you should try your best to comfort her and be kind to her, because even though her life is so bitter, you are still trying to maintain this family, more because you want to protect you, so you must love her. If dad is drunk again, don't fight with him, because that won't solve the problem at all. You and mom can avoid it gently, eat something good for a change, and then go home when dad's mood is stable.
In fact, the atmosphere at home is also a habit. You should try to break the original bad atmosphere and rebuild a harmonious family.
Finally, I wish you all the best and a happy family!