So first off, I'm white, but I'm just gonna throw out there that the trope of the black character dying first isn't about how in a lot of fantasy stories your characters get resurrected. Getting resurrected can happen to any race in any fantasy. That's just most fantasy that you read. People die violent deaths. They come back. Welcome to fantasy.
The negative stereotype in media concerning black people dying so often is about horror and action movies where the black character, who is usually added for diversity as a legal requirement, gets like 4 seconds of screentime before getting axed. It's a problem because it gave black characters smaller roles that didn't pay nearly as well as the leads. They're throw-away characters. But in your story it sounds like this character is a main character...their role is huge, and they don't stay dead. So...perhaps this falls into a different trope, but just because a black person dies in your book doesn't automatically make it racist.
And as far as the white savior trope goes, it isn't really about white people falling in love with black people, either. The white savior trope is about a white person who goes to a native culture, becomes better at the native culture than the natives, and then becomes their king and savior (like James Cameron's Avatar.) If you have a white person who falls in love with a black person and happens to save that black person they're in love with, that doesn't make it racist, either.
It sounds like the witch's race is currently undecided anyway, but writing a mixed race relationship is like...not a negative thing. Especially since it sounds like he isn't really dying for her, but just blissfully unaware he's about to die. And that she isn't so much saving him as going "woops, Ctrl-z" and going back in time to try and change fate. Like it sounds more like a fate story than a race story, to me.
But then again, I don't know the whole story, so do what you think is best, run it by people if you're still concerned before you post.