Alzheimer's

What do you do when your loved one forgets significant events and people in their life? I am just now beginning the journey through Alzheimer's with my dad and I wonder how I am going to be able to handle it as the disease progresses. In June my dad's wife died. He doesn't remember. Every day he questions where she is or makes comments about her as if she is still living. Sometimes I try to just avoid commenting. It seems to be simpler if you don't have to tell him she's dead. But those times when he point blank asks me I feel I have to be truthful. So I tell him. And he grieves all over again. It's like it's the first time he's heard the news. Shortly after the death he would get so angry and ask why no one told him. The thing is, he was right there with her when she died. I've begun to add that part as soon as I tell him she died. I'll say, "You were right there with her daddy. You just forgot." His other thing is he claims the house he's living in is not his own. There's no use arguing with him about it. He won't believe you. We've just started assuring him that he's not going to be kicked out of the house. It seems to appease him at least momentarily.
My grandmother had Alzheimer's. I watched as she progressively grew worse and ended up bedridden and unable to even speak. My mother and aunt had to live with her up until her death. It took a toll on them physically and emotionally. I can't fathom me doing more for daddy than I already do. Is that wrong of me to think that way? My schedule is pretty full as is. And if you knew the whole story of my childhood and such you'd understand more why I feel this way. My son is always asking why I have to tend to my dad when he never did anything for me. It's a hard thing. My dad wasn't there for me growing up. He didn't offer any child support. We did without even the basic necessities of life. But still I loved him. And I would never want to hurt him. I would never want to abandon him in his hour of need. That's what my mama taught me. You help your family. And being a Christian, I feel it is my responsibility to help him and to forgive him.
A long time ago a friend advised me to express to daddy how I felt about what he did to us. I told him, "I can't hurt him the way he hurt me." I didn't want to tell him all that I had kept buried inside. The hurt, the anger, the suffering I endured as a result of his actions. I would never want to inflict that kind of pain on him. But it would be even worse if he didn't have any feelings about what I said...like if he didn't seem to care at all. So I kept my mouth closed. And now, I don't think he'd even understand if I told him.
Every day I pray that some of his memory will come back (he has other issues that contribute to the memory loss). If that could happen at least he might be able to enjoy his life for a while longer. I dread that day when he no longer remembers who his kids are. Oh if only a cure could be found....