What I've noticed about all of these forums (I'm usually over in the "Osteoporosis" forum) is that everyone here surely understands what you are going thru...and are quick to offer a shoulder!
We had the same challenges with our Mother...finally we simply left the TV on all the time. This worked for quite a while until we noticed she paid no attention whether it was on or off. My opinion is that your Dad is somewhat aware...and must be scared...of the changes going on. I'm afraid I would react in much the same manner!
Soon after being put into an Alzhiemer's facility, Mom asked me what she was doing there. (Why ME....there are 6 of us?!?) I carefully skirted the issue for a few minutes, then when she pleaded with me, I told her the diagnosis. We cried together....then she asked me to bring her information. A quick stop to the Alzhiemer's Association nearby provided me with many pamplets to share with family members...and even one written especially for the diagnosed person. Against my brothers advice, I sat and read it with her. I know this would not work for everyone, but it did for Mom. She was STILL angry with me...(many times I drove the hour home crying after being punched, swore at, spit at...etc......but I had to tell myself this was NOT her fault.) Her challenges were more than mine...and she seemed to realize it.
Believe me...you Father is so glad you've taken time out of your life to be there with him!! I would be so proud of you if you were my son!......p