Hey Virginia
I didn't see any grammar issues
As to some of the questions...
2) Plot twists and cliffhangers make you chortle with glee.
(I've changed laugh to chortle, hope nobody minds)
--chortle is great...gives it more personality
6) Your characters (or self) slip on the obvious banana peel.
or should that be "proverbial banana peel"?
--my first thought is 'proverbial'--the sentence seems to flow better, but that's just IMO
Going to be hard to narrow this list down--lots of great ones!
Laura