Your move sounds like a very good idea, Nucking. You tried, the situation is untenable, and you are honoring yourself by changing what you can. Fresia's post put it very well, and I'd echo everything in it.

The first sentence is a real head-shaker. How can one ever live up expectations if none of them "count"?! It'd be funny if it weren't so sad. Chalk one up to irrational and toxic. Your T is right on the mark with toxic. And with what you've described over all your time of trying, there's a whole lot of it. Not discussing your sister's lack of boundaries with her sounds wise. Especially at this time. Toxic people just refuse to see it that way, justify their behavior and turn it back on you. (In my experience anyway.) You just don't need that right now (or anytime really, but especially now!). You're taking such important and positive steps. So proud of you!