First of all, God bless you
You have way too much on your plate right now. Dealing with parents who are not only elderly and in ill health, but are also abusing, must be terribly painful and confusing.
About your Dad...he sounds like he is showing evident symptoms of Alzheimer's. Unfortunately, I have experience with this "A" disease as well, as I lost my Father to it a little over a year ago. When my Dad started to really fail with the Alzheimer's, my alcoholic mother started abusing pain medication to avoid dealing with it. Luckily, their neighbors got hip to all this and called my sister and I to come make some sense out of a totally senseless situation.
Your parents sound like they need some sort of assisted living care. I had to take a crash course in all this when it hit the fan with my folks. Try to access every resource you can, either on the internet or through local organizations. This is a totally overwhelming thing to deal with, so my heart goes out to you as one who knows what it's like to be in your shoes.
Again, God bless. I know how hard this kind of thing is. I will say a prayer for you and your parents tonight.
Peace,
Gabe