I briefly used fusebox 3 several years back when I first learned of FB. I use 5.5.1 now but I have found the build in error handler to be difficult to deal with, particularly when dealing with missing circuits or syntax error in the circuit xml files. What I have done is to use CFERROR in the application.cfm (or .cfc) file and then structure the error page to be stand-alone and included whatever fuses necessary to execute error free. This may take some redesigning of some of the initialization logic for the request, session or application scoped global variables, but it's worth it.
If you have not already done so, you may want to post your question on a fusebox forum, especially since it deals with an old version of FB.