You can add a boot delay in /boot/loader.conf.local (create that file) like: autoboot_delay="120"
But you shouldn't have to. That's really only used for problematic WAN side modems.
If the firewall can connect out to remote sites from the cli but LAN clients connot it's probably a firewall rule or NAT issue at that point.
If the firewall can only reach the gateway and nothing beyond it's probably a missing default route. Make the sure the WAN gateway is set as default and not automatic in System > Routing > Gateways.
What do you do to restore access from the LAN when this happens?
Steve