Hi Becky. Yeah, it looks a little dicey--mostly because it doesn't have too many leaves to begin with and the stem is yellowing. Since you have changed the media and trimmed the bad roots, it sounds like you have done about all you can. If the central stem is yellowing, that's not good.
Does the plant have a large root system? The only thing that strikes me from your pictures is that the pot is pretty large for the size of the plant. And since you're a mister, I'm sure you know not to let water sit in the axils of the leaves.
Maybe it will still throw a new leaf or show other signs that it wants to live.