This config looks good. FPC only needs a single fpc.cfg config file.
Look at the defines for arm embedded.
/home/paul/fpcupdeluxe/fpc/units/arm-embedded/$fpcsubarch/$fpcabi
For FPC to be able to find the right unit-files, the subarch and the abi need to be set correct.
Set the subarch with the -Cp command line option.
Subarch is the name of this directory: /home/paul/fpcupdeluxe/fpc/units/arm-embedded/SUBARCH
Set the abi with the -Ca command line option.
Abi is the name of this directory: /home/paul/fpcupdeluxe/fpc/units/arm-embedded/subarch/ABI
This all looks complicated, but it is the only way to have an install of FPC that can handle different subarch and different abi in one install [AFAIK].