What does forestall mean in paragraph 6

You did not include the text so i have multiple definitions that may go with what you are reading about

Definition 1 : prevent or obstruct (an anticipated event or action) by taking action ahead of time.

Definition 2 : act in advance of (someone) in order to prevent them from doing something.

Definition 3 : buy up (goods) in order to profit by an enhanced price.

The 3rd definition goes more with a text about history

The 2nd is just preventing someone from doing something ahead of time //Example : Back to the Future

The 1rst definition is like the 2nd one but with events.

the sentence that avoid faulty coordination is:

culture, which is well represented in philadelphia, plays a major role including theatre, music, and the visual arts.  

faulty coordination occurs when the writer gives equal importance two different ideas (clauses) which in fact are not equivalent. in order to correct a misplaced clause or idea, the writer can place less important or emphatic ideas in a relative clause as in the previous sentence.