Granny would become a new GHW in the futureNot immediately, but after they return to Norway and conquer the castle. Then, she would lead the two species to co-exist.
The protagonist is Mr. Bobo.I know that in the end the unnamed protagonist (this is for the book, I've never seen the movie) is still a mouse, but this is wild. Perhaps becoming a human again made him a crazy old man. This could explain his ability to communicate with the mice. And of course, his childhood dream was to have his very own Mouse Circus. Also, if you merged the universes, the Other Mother could totally be a Real Witch.
The Grand High Witch's "frying" powers are the same as Matilda's telekinesis.The Grand High Witch was very clever from birth but, like Matilda, left her brain power unused and began to be able to spring rays from her eyes, like Matilda. The GHW, however, was never placed in an environment where she could use her mental capacities, and she kept her power, bettering with time until she could not only merely push or hold things from the distance, but even burn them.
The woman with the green snake wasn't a witch at all.The boy never saw her again, so for all we know, she wasn't at the meeting. And seeing as it was winter and many ladies were wearing gloves, she could well have been a human. Her intentions, if she was a human, are unknown. She could have still been malicious (a child molester, wanting to kidnap him for money, the list goes on), or she could have just been a rather eccentric woman who really did just want him to look at her tame snake. She could also have been trying to prank him, having heard of witches herself.