How do you handle a relationship that feels toxic but you still haven't got closure?

You want closure, I saw it once put very, very succinctly, the disrespect was the closure.
I might add to that if you really need to internalize this idea, if this applies to you personally.
The inability to allow you to express your feelings, without being attacked or dismissed was the closure, the gaslighting and the rewriting of history was the closure. The refusal to come to the table and discuss things like adults, the thousand previous times that the offer was made was the closure.
The refusal to take any accountability was the closure. The redirection of every affront and every assault and putting the blame back on you was the closure.
What closure is it precisely that you're looking for? What you're really looking for is something that is a fantasy, your looking for the person to finally soften, to open their heart and to show some compassion, some empathy, some sensitivity for once. And my friend if that were possible, if that could have happened, why didn't it happen till now? You didn't get it until now, it's not going to happen at your exit interview, so to speak.
All of the evidence, the preponderance of repeated evidence, is all the closure that you need.

Rabbi Shais Taub
Art: NoSo