Let's suppose that I am out of the USA from January 1st 2020 to December 31st 2020 for 335 days of the year.
So I do qualify, but instead of the full ~100k reduction, would I only get (335/365) * 100k = ~91K deduction?
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.