Mary, I echo what everyone else has said. I face some of these same things myself, and I understand how you feel. It does always seem to be one child in every family who is the sole caretaker of a parent. I am the youngest, and the responsibility is left to me also. Difficult as it may be, you may have to just tell everyone "no" a few times, or try to work out a compromise as to when you can do something. I have a feeling, with your Dad and his illness, your mother may be relying on you as the sole provider of her physical needs, as welll as her emotional ones. Try to be patient with her, do as much as you can, but say no when you have to.
As for your father and the hallucinations/apparitions, it is very likely both, as Pandora said. I remember when my grandmother passed away, she took my hand and said "Carrie?" like she hadn't seen me in years. I was 17 at the time, and looked a great deal like her older sister whom I was also named for. I never knew if she was seeing me, or another girl 70 years ago.
I also remember my father's last stay in the hospital, although the medication was attributed, I never really knew for sure. At times, he was talking to young men, encouraging them to go ahead and jump, there was nothing to be frightened of (he had been a paratrooper in WWII), other times he appeared to be talking to his grandmother, who had raised him. Several times, I saw a swirling mist in the corner of the room. Logically, I told myself it was a trick of the sunlight, but the nagging doubt remains.
I do think as people are in a weakened condition, relatives and loved one's spirits come to them. I certainly hope so.
Hugs to you, my dear Mary, keep your chin up and please remember to take care of yourself also. You are loved by many. =)