I am so sorry to hear of all your struggles. First off you came to the right place. The people that come to this forum can find so much good advice and geniune concern and compassion.
I myself, recently joined this forum because of my depression. You see, my husband is an Alcoholic and I can't tell you how much being here has helped me.
Please understand this. Your father doesn't know how to be anyone else but himself. You sound like you have so much compassion. I believe the Lord sent you back to his home for may reasons. First, because you needed help and next because he didn't want you to use your pain, both physical and mental, to turn out like dear old dad.
You are very lucky to be here telling your story, but there is a reason for that. Sometimes doctor's with pill bottles just can't always help. You should get yourself in therapy and God only know's with what you've been through you could probably use it. Then you should pick up your bible. Jesus is there listening, he's just waiting for you to ask for his help. I believe this with all my heart and that sir, is what has gotten me to you.
You never ever forget, you are already a good man. You have proven that by putting you out to us on this forum.
Try this, this is something I have learned very recently. Go to your dad and give him a pinch on the arm, ask him ' what do you feel like doing right now?' Let him respond. Then put your arms around him and just give him a meaningful hug, just say thank you dad for being here to help me. When you give a pinch, you get pinched, when you give a hug, that sir leaves no room for anything else. You and him may then come to a different place in your relationship.
Best of luck to you and my thoughts and prayers are with you and your family..
Always look to your past to better your future