Percentile formula w/ 4 diff logics (multiple criteria)

Hi

Looking for help with percentile aggregation based on 3 different methods.

I have offices listed in column I, column O shows value for each row item.

in column Q, i would like to show, 20th, 40th, 60th, and 80th percentile ranking applied to 25% of each population. So, bottom 25% will get 20th percentile, 25% population will get 40th percentile...top 25% will get 80th (exclude 0s and blanks)

in column R, same as above logic, however, it's based on 17th, 33rd, 50th, 66th and 83rd percentile and based on 20% of population per bucket (exclude 0s and blanks)

in column S, same as above logic as well, however, broken down by 7th, 50th and 25th percentile, and it applies to 1/3 or 33.333% of each bucket. So meaning, bottom 1/3 of population will get 25th percentile ranking, mid 1/3 of population will get 50th percentile, and top 1/3 will get 75th percentile ranking

I have attached the spreadsheet.

column P has this formula - it shows percentile of 90th, 75th and 25th (exclude 0s and blanks), however, if values fall below 25th percentile, it shows "", when i would like for it to show 25th ----> can this formula be modified to use for above renditions?

{=IF($O14=0,"",LOOKUP(PERCENTRANK(IF(($I$14:$I$960=$I14)*($O$14:$O$960<>0),$O$14:$O$960),$O14),{0,0.25,0.75,0.9},{"","25th","75th","90th"}))}

thx