Oldbatty, I'm very sorry to hear of your dilemma. Sadly I think this is being replicated across the UK, with thousands of people in their 60s, 70s (and - gulp - sometimes even in theit 80's?) having the care of, and worry about, their aged parents. I think that a major problem is that many of our aged parents had no experience of having these problems because their own parents had died well before they (our aged parents) reached 50, (or even 40.)
My mum is 94 and my elder sister (70) has the day to day worries, and all that this entails. Thank heavens our mum is now in an excellent care home. But our mother has dementia and she's frequently grumpy, rude, demanding, and difficult. Nothing is right and everything is contradicted. Visitors who are non-family are treated with much greater politeness, so there's definitely an element of awareness going on here. (My sister found having counselling to be a great help.) I offer support from a distance but I appreciate that the burden of care often falls to one family member. You must be kind to yourself about this. Even with them living so far away, I suggest that you keep your visits short. (Can you stay somewhere overnight, so that you make one short visit on the day of your arrival, then another on the next day, before you depart?) Some people won't agree with me, but my own view is that we "owe" our parents nothing (we didn't choose to be born). Do look after yourself and don't feel guilty! .