Rock what professional support do you have for your own struggles with depression?
How come it is difficult to talk to your partner? And do you have friends you can talk to about this to spread the load around?
Sorry for so many questions
It is sad to read about how your parents are, but you really aren't responsible. It sounds to me like your dad had a second chance and threw it away by using what happened to you as an excuse to go back to his old behaviour. This is also not your fault. Parents are supposed to protect their children and you clearly suffered emotional abuse from their behaviour from then until now and it hasn't stopped.
I would suggest getting extra support for yourself at this time and distancing yourself from your parents to be able to cope. Especially during xmas when the drinking will be worse. You have to protect your own family and yourself now.