What prior notions did the pilgrims have about the Indians before meeting
them?

They did not know many things about the indians. They only knew that they were very different from them, looked different, had other customs, and had a different religion.

Precisely because of this last aspect: religious differences, the pilgrims did not have a very positive opinion of the indians. Pilgrims were very close-minded, because they believed that the calivnist version of protestant christianity was the only valid form of religion.

repetition is used to make the poem come off the page

yes yes it does !