for one thing, PFPOSTPRINT=printwizard.exe is probably not good enough for printwizard.exe to be found.
set the full path to the executable.
e.g. PFPOSTPRINT=\printwizard\printwiz.exe
along with any command line arguments you want to pass to printwizard
filepro will add the print-file name to the arg-list you send to printwiz.exe so you don't need that.
also make sure none of your processes, formats, or command line arguments to *clerk or *report override printer destination - there is a heirarchy of what overrides what, but i do not have it handy. how did you set "printer maintenance" to pfpostprint exactly?