How do you handle an elderly parent who is not only displaying all of the normal "bad behaviors," but is now refusing food, meds, and care?

My father has Parkinson's (diagnosed in 2005) and the beginnings of Dementia (not technically diagnosed, but become more and more evident on a daily basis). He took a fall in his assisted living home and was hospitalized. Since then, his personality has completely changed and he has gone ballistic, yelling, screaming, thrashing, kicking, cursing, saying horribly inappropriate things, etc. He is convinced that the hospital staff is trying to kill him, that he has been kidnapped, that no one will help him, etc. He has had to be sedated and restrained (arms and legs) because he keeps ripping out his IVs and kicking and hitting the nursing staff. Today, he decided he was going to refuse everything - he won't eat or drink anything, he won't take his meds, he won't let them take vitals, he won't let them draw blood for labs, he won't let them do any physical therapy ... nothing. The one time they did take off the restraints so he could stand up to use the urinal, he tried to make a run for it and basically flung himself into a wall. They need to run tests to get to the bottom of his blood pressure fluctuation problem (which they believe is causing the dizziness that led to the fall - one of several falls over the last couple of weeks). An echo and an incomplete nuclear stress test showed the possible need for a heart cath, but he won't cooperate with any further tests to get a definitive diagnosis on either problem. We have been told that in all likelihood, he will not be able to go back to assisted living, but instead will need to go to a rehab or skilled nursing facility, which will seriously make him totally lose it. We are at our wits' end? What do we do? Oh, and this is all my fault - I am his oldest daughter - the only person willing to take on caring for him - and all of this is my fault.