Well, "insane" is more of a legal term that I don't like.

My father still refuses to grow up and take responsibility for living life to the fullest. He has been a severe alcoholic my entire life and I'm in my twenties. I do not think he will ever quit, and that is his choice.

We do not have much of a relationship because of it, as I'm sure you can imagine. He lives in another state which makes putting distance between us easy. He remarried a codependent wife after my parents divorced who buys his alcohol for him for fear that he will get angry and possibly hit her (I suspect, as that is how he behaved toward my mother).

I have no fear of becoming an alcoholic. I don't even fear my father dying, as I am well aware of the path of destruction that he is on and where it leads. My only real fear is of not living life to the fullest...

I do not think medication works well for depression long term (if at all). It can take the edge off of it sometimes, but unless you have therapy with an effective therapist and you actually take responsibility for change will it end. Depression is not a life sentence. It is curable.

I would suggest to stop looking to the past as you know what the issues are there. You've undoubtedly discussed them. I really don't think you will behave like your father since you are aware of his issues and I'm sure aren't eager to relive them.

Instead, consider as to how can you change the here and now and live more fully in the moment?

Do you like your job?
Are you in a satisfying relationship (if not, how can you make it satisfying)?
Do you like where you live?
Do you do things that are enjoyable?
What things would you like to do with your life? Visit any certain country, etc.?