I think that if the miles-to-empty display is still working, your fuel sender must be working okay. I would suspect that the problem is with the actual gauge in the instrument cluster. I’ve never had a Nissan, but the miles-to-empty displays on all the cars that I have had, have been very accurate. I would guess that you are safe to just go by it. Frankly, I just use that display/warning and hardly ever look at the fuel gauge anyway.