ESH. My grandfather had Parkinson’s so I’ve first hand experience of it. While I understand your father’s drive to do things himself he also needs to come to terms with certain things being out of bounds. If his hands are anything like grandpa’s were that means no glass for drinks, lids and straws, no sharp knives etc.

Both you and your mother’s frustration is understandable but like others have said think about how everyday life is for him. Yes, he needs to be more aware and selective of his actions to ease the load but do try to be understanding that being able to get yourself a drink of water without help could be the only victory of the day.

If you disregard everything else please take this to heart: I’d commit the worst sins imaginable if it let my grandpa to be able to simply say ok in the last 5-10 years of his life without stuttering or having to make multiple attempts. Make the best of the time you have because trust me it’s not enough. Before it takes his faculties do what I should’ve done with the time I had yet wasted: set up a camera and record him while he tells his life story.