Jeff
you have two option
first and better one is to set up your BOM for 2.500 KPC so consumption quantity would be 1 EA.
the other one that we have used in our projects is to create a delete standard "PC"/ "EA" and create new "PC"/"EA" by copying from Kg. in this way PC will accept decimal place and there is no need to change UOM of previously defined materials.
regards
Samira