1) You can totally see each house in one night with Express. You might not see all the shows, sample the food, experience the scare zones, or ride any rides, but you can do it.
2) STAY AND SCREAM IS ESSENTIAL. The opening ceremonies is usually just some sounds and maybe a few chainsaw people vs being in line for you second house of the night.
3) No, you're really at the mercy of scare actor timing.