Can I change the port/path to use a single 1090 dump file?

YES, there is a very easy way. Please see item (3) QUICK METHOD below.

The detailed answers are here:

(1) Flightradar24 Forum: How to Feed Data to Multiple Sites - A Brief Guide

(2) This Forum: Bake a Pi, Additional Feeders
Scroll down to “2) INSTALLATION OF FR24 DATA FEEDER:
Further scroll down to “Post Install configuration/Re-configuration of FR24 feeder

(3) QUICK METHOD (if you don’t want to read above posts):
Type this address in your Browser
http://< IP of PI >:8754/settings.html

On the settings page opened, set the “Receiver” and “Host/IP” to any one of the following two:

Receiver: ModeS Beast(TCP)
Host/IP: 127.0.0.1:30005

OR

Receiver: AVR(TCP)
Host/IP: 127.0.0.1:30002

Hit “Save” button at bottom-right of page, then hit “Restart” button next to it.
Wait for some time, status page will appear. Initially it will show nothing working, but after a minute or two reload it and it will show everything is normal.