I had subscribe 5 x Fixed Public IP Address for my home lab, and please refer to the following steps on how to assign all public IP to a single WAN Interface
login to pfSense, and go to “Firewall” > “Virtual IPs” > +Add
Select “IP Alias” , Interface = “WAN” and specify the IP Address and Subnet Mask
You can select the new Public IP Assigned for NAT configuration now.