I think with all you've been through these past years that we accept your parents are unhealthy. Expecting them to act in a healthy manner would be like expecting a puppy to stop chewing. It's just not in their nature. They are the way they are. Being upset about it won't change them. Yelling or pleading or begging won't change them. They are the way they are.
You need to either get into a mindset that you let them be puppies, and it doesn't bother you, or you move out. I don't see any other option.
You can't negotiate with puppies. Even if they say they'll go on vacation, they'll just change their minds. It's what they do.
If you have money to send THEM on a vacation, send YOURSELF on a vacation. Do you have somewhere you can go? Then go there. You absolutely need to shore up your own strength, for your path ahead. It's time to release them to be puppies and to take care of your own health.
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