What do I do? My parents will/can not follow medical instructions and I've given up.

I live in Canada and my parents live in the US. I am within driving distance - it's a 4-5hr trip down. I am married and we have three kids who are not babies but still young - 10, 10 and 13. We have no relatives or friends here who could take my kids for any long period of time and my spouse has a very intense job where he is "on call" 24/7. I have to raise my kids. We used to visit my parents on a pretty regular basis once every three months or so. I phoned and they phoned us - all the time. Then my dad's health declined and bit by bit they no longer want me or my husband involved - we are seen as interfering. This after multiple times of dropping everything and racing there to help them. I have a sibling who lives in the same town as they do and he is not reliable. They don't like it when I ask nurses and doctors questions. The kind of questions you are supposed to ask doctors and nurses when your parents have arrived by ambulance. Nothing out of the norm. I used to ask my parents about their medications, their eating (my dad is a diabetic who does not eat appropriately), etc. No more. I am persona non grata. Lately we are in a Groundhogs Day scenario. My dad has an incident - lately a diabetic coma, or a fall where he ended up OK, and a fall where ribs were broken. He is pretty much confined to his chair because he is wobbly on his feet. After a hospital or rehab hospital stay - they eventually "dismiss" the home care people; stop doing the physical therapy, and send the nurses away and begin eating junk food and things which a diabetic just should be limiting if not eliminating entirely. He goes into a hospital, comes out, an incident happens, back in the hospital, and on and on. Lately both of their cognitive abilities have been poor - my dad thinks he's back in 1958 sometimes. My mom can't remember what yesterday's trip to the hospital resulted in which diagnosis. They are either lying or they just can't keep it all straight. Sometimes both at once. He won't wear his hearing aids and she lies. My sibling is trying but does not have the capacity to understand much of this. He has his own family as well. After the last hospitalization (broken ribs) and subsequent trip to the rehab hospital - my dad came home and not two days later my brother has then back into the hospital. My dad's insulin was fine but he was dehydrated. I've lost track of how many of these same scenarios we have had. In the last year+, my parents no longer call us. They no longer ask about their grandkids, send birthday cards to them and pretty much have told other relatives that I "ask too many questions" and my kids riffle through their things when we visit - they do not. They sit, they smile, they speak and they are polite. My two youngest are afraid of their grandma - she's just mean. My dad will point blank say in front of my kids that "our life is none of your business" directing that comment at me. We have spent nearly $30,000 or more I've lost count trying to help them renovate a bathroom to make it safer, to get them furniture that they can actually sit in and get out of, meals delivered in so they get some nutritional food in them. We were supposed to visit them briefly (we always stay in a hotel) in the next couple of weekends on our way to visit other family friends. I finally just phoned and said we would not be able to visit them. I told my husband (a saint) that I can't see how driving all of us down there for a 9:30/10PM arrival where we would go to sleep in the hotel, then get up and visit them for about 30 minutes before they just stop talking to us and stare at us. They also refuse to eat a meal with us - they only eat junk (donuts, fast food, etc) so our "healthy" i.e. normal eating - we might bring in breakfast like pancakes, eggs, etc to eat as a family - was flatly rejected on their last visit. Three times we brought them food to share and three times it was placed in their fridge lost to time. I have three kids to raise; I have a marriage that I enjoy; I want to share my life with my parents but they don't want to. I began to throw in the towel with this last phone call. I'm not sure what else I can do. I can't be their guardian because I live out of the country. My brother couldn't manage it because he's not that kind of guy. Leaving their home is not an option. They would rather die broken and incoherent in their home than move to a facility. I'm lost and exhausted. I have become a child that I never believed I would become.