FPAC is run from the fpac.sh file.
This file creates a shell to give to fpac and fpacstat the needed environment. It includes a PATH to the bin directory of the fpac binaries.
To start fpac, only run /usr/sbin/fpac.sh from your rc.local or start-up file.
There is no need to add a & (ampersand) at the end of the line.
fpac.sh must be run after the ax25 layers are fully initalised.