IDS/IPS with Dynamic IP and NAT? Ruleset for Port Scans?

[Deal18]

So I have been reading up on how to setup Scuricata on my OpnSense box at my house.  From what I have read I need to put my WAN IP into the "Home Networks" section.  The issue is that mine is a DHCP given address.  I can't put a hostname into the field either.  Is there an easy way to automatically keep my WAN ip in that list?  Thanks.

Also is there rule set for port scans?  I have looked through ET Telemetry, Snort VRT, etc.  I can't seem to find a pre-made one to detect port scans?  Thanks!
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