Is the FEIE tax reduction, based on Physical Presence Test, prorated based on how many days you were outside of the country in the year?

Since you were out of the US for at least 330 days in the 12-month period of Jan-Dec 2020, you qualify for the Foreign Earned Income Exclusion for that 12-month period. (Note that the 12-month period used for the Physical Presence Test does not have to be Jan-Dec, and you can use multiple, potentially overlapping, 12-month periods in a calendar year. But in this case, the Jan-Dec period works.)

Since you qualify for the FEIE for the whole year (under the Physical Presence Test or the Bona Fide Residence Test), you get the entire exemption of $107,600 for 2020. You would only get a "partial" exclusion if the periods under which you qualify for the FEIE under the Physical Presence Test or Bona Fide Residence Test did not cover the whole year; e.g. you were out for 330 days in one or more 12-month periods, but those 12-month periods were not able to cover all of 2020.