Turn the modem on, wait 10 minutes then turn on pfsense router. Is there a setting in software I'm unaware of that is preventing my router from acquiring a Wan IP from the modem?

Just go for a small PFSense box, I think they go for around $200 - $300 for a decent one. Keep the old router around as a fall back if needed.

When taking steps to ensure network security, the pfSense firewall solution and Netgear routers are top choices. Compare the key features.

If your ISP router was the kind to never get updates or security patches, then you'll almost always be safer on your own OPNsense or pfSense platform, but you still need to keep on top of your ...

Even if you're happy with the router supplied by your ISP, building your device is a cool way to see how everything connects and what the router and firewall are tasked with handling.