Demented father's behavior--impulse or planned?

My 80 yr old demented father has had his second stroke. He moves all body parts, but his speech isn´t coherent, he does answer questions at times and listens when certain people are speaking to him, but isn´t doing well cognitively.
He has always belittled me and has demonstrated much hate for my person over the last 5 years or more; I am not a sunshine girl, but am caring & have been to his rescue many times!
Now that he´s bedridden, he cooperates with all the caretakers, and enjoys my sister´s care as his primary feeder; she uses child psychology to get him to eat & it almost always works. My sister and I work together to care for him when the homecare women are not around; I usually do the care while my sister conforts him and holds his hands so that he doesn´t HIT me.
His eyes are always wandering and checking what I´m doing, we have seen him many times getting ready to hit or kick me...this happens every time I have to go near him. When he´s not trying to hit me he is talikng about me in a derogatory way, never a positive word. Yesterday, right after the caretakers left, I brought him near the table so he could eat with his right hand which was unrestrained. When I got close to put some fruit near him the rt hand raised to hit me but I grabbed it and attempted to tie him down with him resisting the whole time & trying to dig his nails into my hand...after I managed to tie his hand he viciously gobbed all over me a couple of times.
These horrible behaviours are all directed at me; he may occasionally tell my sister that she knows nothing, but it´s rare and she always laughs it off.
I know that demented people only remember the past & their hates resurface with a vengeance as the dementia worsens, but my father´s actions are studied and deliberately aimed at me; he acts beautifully with ALL the caretakers; I do not believe that his actions towards me are merely an impulse!
We are thinking of sending him to a rehab facility, but have no idea how long it´ll take to get a bed for him.
I have often wondered if his dementia isn´t the result of a major depression since he lost his favourite daughter 11 months ago!
All feedback appreciated.