Dad is depressed, financial troubles, don't know to help. Help

My dad has been diagnosed with depression after he lost his job to the financial crisis back in 07'. His girlfriend who has bipolar broke up with him 3 months ago after she entered a psychosis in which she developed delusions which lead her to believed that my dad was a physical threat to her 3 daughters (which was not the case).

Now we are living at my grandparents (his parents) house which is very small while the tries to get back up on his feet. We have been in and out of my grandparents house 3 times since 07' as his last girlfriend was one out of two ex girlfriends houses that we had lived in.

Dad works as a bank manager. He is still waiting for his ex girlfriend to come out of her psychosis. he keeps in regular contact with her parents and her psychologist. My dad is a very stubborn person. The last time i suggested the the relationship was not feasible, he got very angry and upset.

He drinks every night after work and smokes that synthetic weed crap. I try to spend a lot of time with him and I feel guilty when I go out. But sometimes when we hang out we don't talk, and I feel he is deep in his thoughts. I come from a family of crap communicators so it is no surprise that he does not open up to me and is very withdrawn. He looks so down all the time.

I want to know what to do? Please

How old are you?

I am 18 yrs old