Are there situations where it is wise to remove oneself from parents? My philosophy is to set an example to others though the path of a bodhisattva. What would the buddha advise to someone considering reducing or eliminating visting a parent that causes emotional distress and fear after one has tried to practice patience, acceptance, acknowledement that this behavior is coming from their own suffeirng, metta practice, meditation, along with trying different ways to communicate so as to not arouse negative statements to an adult child? Also, a reference text, if any could be appreciated. Would distancing onself not be in accordance with the path of a bodhisattva?

These dynamics have always existed and it has become worse. Recently the sibling of this parent that distanced herself years ago from this parent and validated the narcissistic behavior of this parent.

In this specific situation and which is a factor in the level of difficulty dealing with this parent is that the other parent requires 24 hour nursing care at home and is unable to care for herself (including the inability to communicate).  The other parent/caretaker has refused to disginate the next of kin (adult child) living in a reasonable distance from their home in the event that something unforeseen happens to the caretaker.  Even a short hospitalization would require someone to step in immediately.  The rationale has to do with the fear of not being in control with money. After trying to assure this parent that this is not about money, rather the other parents coordination of outside care, in different ways and at different times, it is met with cruel, untruthful statements about the adult child that is willing to step in. The response also included a statement that if something did happen he didn't care if the estate all went to the State. Again, money and control of money was not mentioned to this parent.  This parent was told by the adult child that the statements were hurtful and not true. The response from the parent was that it was not his responsibility how this adult child felt and would not take any responsibility.

The fear and emotional distress mentioned above mainly is the result not having an emergency plan in place and second the acknowledgment of the diffence in character, values and feelings of loss of both parents. Exposure to this parent tends to water the unwholesome seeds of unsatifactory feelings of this adult child.
When offers of help are denied, one has done what they can. 
I'd say a temporary distance is acceptable in this situation. 

For the adult child of the sick one, maintain the intent to help and the compassion and bodhicitta for both parents. 

This is a rough time for all involved, in times like these emotions tend to cause conflicts that might seem to be about one thing,  but are actually about the emotions caused by the looming death of the loved one. 

To the adult child my advice would be as follows :

Try not to take things personally here.
Drop off care packages for both parents. 
Make sure to let it be known (in a positive way, text or short polite letter) that if you are needed you are a phone call away.
Do not worry about or mention next of kin.
Remember that others actions and words are not an excuse to "Water unwholesome seeds" 
Do not hold a grudge, and give yourself as much distance as you need. 
After the parent dies, if the remaining parent needs it, be there to comfort and ease the grieving process. 
Reread all the branch and root Bodhisattva vows, one by one, and ask yourself where you are doing well for each vow, and how you could improve on each vow. 
Remember that the vows apply to all beings, not just family. Treat yourself to some ice cream and some activities you enjoy. Spend time with friends. 

This kind of situation is an incredibly difficult one. For everyone involved. 
It can be trying and emotionally draining.
I do not know the full situation, only what is in the question. I've tried to keep this advice in line with the Buddhist tradition and Bodhisattva tradition to the best of my abilities. If there is some error please comment and I will edit accordingly. 

I hope this helps.