Appropriate use of commas

I am taking an online writing class and the teacher keeps harping on my use (or lack thereof) of commas. Personally I think she's crazy. I'd love a 3rd party's opinion on a few examples. In the following two examples which answers are correct?

1a)
Throughout the film [comma] a narrator will recite short excerpts from the letter to provide cohesion and to carry the story forward.
1b)
Throughout the film a narrator will recite short excerpts from the letter to provide cohesion and to carry the story forward.

2a) In the following few pages [comma] I’ll try to give you a sense of how I envision the film.

2b) In the following few pages I’ll try to give you a sense of how I envision the film.

Here were her comments:

Do watch your comma mistakes, but, thanks for making at least one mistake so I can teach you something: always use a comma after an intro phrase tells when or where something happened, or gives the set up for a sentence.

Even here I think she added at least one too many commas (after the ‘but’)…

Am I crazy?