Which example from "a visit of charity" speeds up the pacing of the story and
makes the reader feel as if the action is happening quickly?

Irony and a metaphor is the best answer to this

Then something was snatched from Marian's  hand - the little potted plant "Flowers!" screamed the old woman...

Explanation:

It proceeds with the story, it is not very descriptive.

The sentence, "After trying the new recipe, chicken pizza tasted delicious.", contains a dangling modifier.

The phrase, "After trying the new recipe," expresses an action but has no doer. So, we look for a 'doer' (or more properly a subject) in the clause that follows it ("...chicken pizza tasted delicious."). "Chicken pizza" can be a subject, but since it cannot perform the preceding action phrase (i.e. trying the new recipe), we cannot use it as our subject for the phrase.
Thus, the phrase, "After trying the new recipe," is a dangling modifier. 

Hope this helps.