I intend on incorporating this characters into my 'Queen of Sorrow's Falls' series, should I ever reach the point in the story where they would become useful.

I see what you're getting at; how I left it is rather ambiguous, but I think it works for a story of that length.

1) I'd be too scared to do anything with her.
2) Hmmm....
3) I think Gertrude's students would be too afraid of her to ever try anything that severe.
4) Yes, I think the ending kind of goes both ways. Brian learns to discipline his class effectively, but he is now further under Gertrude's control. Brian is slightly submissive, but not enough to actually enjoy what Gertrude was doing to him. So, Brian is rather pleased with the ending.