That is mighty strange! Too high temps will indeed shorten the incubation period, but I'd imagine with temps that high that the fetus would rather die. With too high temps, I've had ducklings hatch at day 31. Still a way to go, though.
It seems your duckling hasn't read the manual, and will emerge whenever it pleases. Keep candling and checking on it. They use a long time to get out, so even if it seems ready, it will most likely still be days from hatching.
Are you able to post a picture here of you candling it? Would be interesting to see what's inside!
You really should try to get that temp down in any case. Can you make a hole in the incubator to let outside air in, like let the lid be slightly open or something?