I think the queen can quickly lay one egg in an emergency without the need for an eggsac at the time as there was no way she could've created one on the sulaco in the short amount of time she was there. Also in answering ur other questions here u go:
first of all, the superfacehugger dies after the second impregnation is complete to my knowledge, the first impregnation will become a queen, the second will become an adult alien created to guard the queen until she has birthed & begun to lay more eggs.
second, it is usually aliens which are not in the prescence of a queen which produce a single superfacehugger egg which then births the superfacehugger, but since the queen layed a superfacehugger egg on the sulaco, then I'm assuming they can produce one in an emergency, but this one probably wouldn't become a queen unless the queen which produced it died.
third, normal facehuggers cannot create queens, if the facehugger was not in the prescence of any adults or a queen, then it would still become an adult, then produce the superfacehugger egg