The later errors are meaningless, they’re just an outer script/executable notifying of failure because something they invoked failed. The first error is always the cause.
If the output is still the same, then the 8.1 SDK has everything to do with the exit. It’s telling you that’s why it failed. If you installed it, then obviously Unreal isn’t finding it where it expected to. I don’t know why that would be or how to fix it, but that’s the issue.