Dear Painter,
In my family, it's my mother who has PD and my father is her primary caregiver. I'm an only child and secondary caregiver. In addition to my mother's daily struggles with this debilitating disease on all fronts (physical, mental, and emotional), there are also my father's issues with frustration, anger, depression, and "burn out." So, believe me, I understand the every-increasingly difficult situation that you are in and can relate to the changes in your family dynamics.
Without knowing more about your situation than what you've written here, I would say that your mother may want your father to remain as able-bodied and independent for as long as he possible can. Doing things for himself -- for example, making a sandwich for himself -- means that he is required to move physically (moving around in the kitchen or, if his mobility is already severely limited, then at least moving arms and fingers), work on his mental processing abilities (brain-to-hand coordination), and feel empowered to be able to still do certain things himself even as his body (and, perhaps, mind) are starting to fail him. Your mother may not expressing this desire for your father's independence in the best of manners since fear over her husband's decline mixed with her own physical and emotional exhaustion may lead her to get upset at you and your sister.
How familiar are you with Parkinson's Disease? I agree with Duke in his post. The web site
www.pdf.org is an excellent resource, whether you're new to PD or not. There are also some terrific books that you can read. Since my mother's diagnosis, I have read everything about the disease that I can get my hands on, both on-line and in hard copy. If you want/need a quick-read, in addition to the PDF web site, I'd recommend reading at least "Parkinson's Disease For Dummies," also a very good resource. I wouldn't stop there, though, since the sooner and better you understand the complexities of this disease, the better you can help and the less your own frustrations. While much emphasis is placed on motor skills, it's important, too, that you understand the cognitive impairment that becomes part of the disease at some point for most people with PD. Such changes can be very subtle and mild, ranging from problems with processing certain information and decision-making to periods of apathy and anxiety or depression. It saved us a lot of drama to understand that such changes in my mother were part of the PD and not any sort of games of manipulation on my mother's part.
With respect to your mother's remarks to your father, I wouldn't completely rule out attention-getting since the caregiver can be neglected as all attention is focused on the person with PD, but I believe it's more a matter of letting off steam. She is frustrated and burned out and, like my father, is "no longer herself." PD doesn't just assault the person with the disease; it also gravely impacts those nearest and dearest. While boundaries of acceptable behavior need to be in place, I have learned to roll better with the punches when my father lashes out verbally. As things become more and more difficult for your parents, the need to be "the calm in the storm" for them becomes more and more important so things don't escalate unnecessarily. I suggest that you and your sister encourage your mother to leave the house and do something enjoyable for herself a few hours per week, either alone or with her friends (i.e., away from family), during which time you and your sister can take turns spending time with and caring for your father. Most of my father's frustrations and outbursts boil down to his desire for some quiet time to himself....and a need for more and better sleep.
As for your concern about whether your mother is depressed, that surely may be a factor in all this since, after all, she is going through a very difficult time in her life and in her marriage. However, that is a question best left up to her and a qualified physician to answer.
You also raised the issue of assisted living. There are several good articles about this topic available on this web site that you may wish to check out. Again, it's difficult for outsiders to answer this question for you since so much goes into reaching such a decision, although I'm sure you'll receive valuable input from others. In my family's situation, my father and I have discussed the various options, and I have provided him with information from my research. I see my role as that of advisor and listener, not decision-maker with respect to my parents' marriage and lifestyle. My father knows that I'm here to help with making arrangements for adult day care for my mother (something he is finally coming around to agreeing to), in-home third-party care when he/they are ready for such, and eventual assisted living or nursing care when that time comes. Letting our parents know that we're here to help them rather than push them into something or hinder their efforts to remain independent or contribute to the drama ourselves is a gift that we can give to them during these difficult times in their lives...and ours. Perhaps you can start the family dialog by sitting down with your parents and sister after doing some research into available options (so you're well-prepared for questions and possible resistance), getting everyone comfortable with open dialog about such issues on a periodic basis. Personally, that first conversation with my parents was the most difficult, especially with respect to my father who saw it as an infringement on his independence on the part of his daughter; now, two years later, we have periodic conversations without conflict, and my suggestions are better received.
Hard as one tries and no matter how much one reads, nothing helps prepare a person for the sadness of losing one's loved one and the frustrations involved in being relatively helpless in stopping its progression, even if it's a slow process over many years. I hope you and your family can grow closer with time; you need each other to get through this. I'm here if you have questions or feel the need to vent. Best wishes to you and your family.