Caring for a Duck Egg?

Yesterday I found a single duck egg in my neighbor's backyard. He had been doing some yard work and there was no mother in sight. The egg was cold, so I brought the egg inside. I'm not even sure it's a duck egg, but it seems like one. I'm not exactly sure how to car for it. I placed it in a small bowl thing with a dry washcloth around it in an old hermit crab cage. I placed the cage in a cupboard with a desk lamp hovering above it in the cupboard. I periodically spritzed it with warm water and turned the egg a bit, as it said to do on various websites.

Today we bought a heat lamp because I felt the desk lamp wasn't producing enough heat. Now I have the egg sitting in a warm moist towel underneath the heat lamp. I have already tried the flashlight trick to see if the embryo is even living and there was a small reddish area near the top side of the egg. Am I taking good care of it? Does anyone think it is living? Should I spray it with water or keep it in the moist towel? Is there any way I can find out how old it is? Thank you!