WB already killed Superman in Batman v Superman. Killing him again in the DCEU would be redundant. They only way it could possibly work is if they reboot Superman and not have him part of the DCEU.
Not that I recall. He was weakened by the kryptonite island, but I don't think he died. It's been a while since I watched Superman Returns though. BvS is the only time I recall him dying in live action.