My dad is going crazy?

Just two days ago, my dad was the happiest person alive. He made dinner, he was singing, humming... Then yesterday, he wakes up, and screams at me for no reason, then comes back home from work hours earlier. (No he was not fired, he is the owner) When my mom comes home, he doesn't even greet her, and walks upstairs with 5 cans of beer. My mom skips dinner and lays down on the couch, but I don't blame her. My mom is the owner with my dad and wakes up at 6am every morning, and comes back home at 7-8pm. Furthermore, she is a very sick person, who has to regularly work out 2 hours a day, she even works continuously in the weekends even though she's butt tired, and yet she rarely complains. Today, I woke up, and kissed my mom good morning, as she left at around 7am. My dad, who woke up at 10am phones my mom and screams that the shitty phone isn't working and blames my mother. I am so sick and tired of his roller-coaster attitude, and feel so sad and pity my mother.

My dad drinks a lot, plays a lot, barely helps my mother. However, I know my dad still cares for the family, and can sometimes see his love for the family from time to time. Is my dad normal? Do you know whats going on with my dad?