I don’t think there’s anything that could’ve been done differently really for this particular egg - look how far you got with it! But I also think that the odd substance on the top of the membrane was something growing. There was the video someone had posted (I think it was the Japanese student one? It was the one where they used a cup and the Saran Wrap and tossed the shell) but they also had added a disinfectant to the bottom of the cup, I assume to inhibit growth of bacteria and fungi. Because in the grand scheme of things, your little ET was basically an egg with an XL crack in it. Haha. I would think as sterile a situation as possible would be the way to go with open ended eggs. Potentially spraying everything down with isopropyl alcohol and letting it dry prior to setting it up? I may have to join in with something like this if I can source an egg I don’t care too much about... lol.