If you put that port in the firefox proxy settings, then you should put that port in the redirected ports and that should take care of it, hopefully without unchecking the Ignore local communications.
Monitor the real-time shields, web shield details and ensure that the traffic is being scanned, e.g. the scanned count would be increasing and the last scanned field would also be constantly updated.
If not then you might need to uncheck the ignore local communication again.