Farview, you are overwhelmed because you are exhausted. You have received bad news about people close to you, are living with an ill, demanding and mean husband, are used to doing the lion's share of running the household and doing D.I.Y; yesterday did two hours dog-walking, a supermarket shop, batch cooking, hoovered the entire house, and fed and entertained three/four grandchildren. Your house and its situation clearly are important to you, but there are other people who could do much more to help. Your husband should pay for a cleaner and window-cleaner and some care; your grandson could help with dog-walking and cleaning, and your adult children could start finding out about help available for you and your husband.
That said, I am aware it is much easier said than done; help is available but accessing it is difficult and time consuming; trying to persuade your husband to fund help will be difficult, (memories of same with my father) and your adult children probably have no idea how exhausted you are.
You do need to call some sort of conference and ask for help; you are doing far too much and being taken totally for granted.
Sorry; this is not for your fault; you clearly have high standards and I think your family is taking advantage,