CMB, I wouldn't have assumed that when trying to piece it together but hey, that's good enough for me.
Sorry to keep this thread going but while following your solution to use a manual WAN rule on top to drop the noise, I found a reason not to be in a rush over this…
1. I Created a new rule to block the specific private IP (broadcast) source address; as expected the 2 system rules found on the WAN tab (enabled by check-box) remain on top but there seems to be no way to relocate my new manually created rule to the top of the heap... so...
2. I released my ISP assigned address on my WAN... (or just unplug the WAN)
3. Then I deleted both system WAN rules (block private IP's and Bogon Networks)... now with only my manual WAN rule still present...
4. Went back to the WAN tab and reselected the block private IP's system rule and it immediately populates itself right back on top of my manual rule... I was afraid of that.
So that means I will need to create replica's of one or both system WAN rules manually starting with 3 separate rules to cover all 3 private IP ranges/RFC1918. As much as I appreciate your suggestion, for now I'm just going to stick to the system (default rules) and work around this with a syslog daemon and hopefully a filter to not re-log traffic from that single broadcast gateway (source) address... Thanks again! Any general knowledge book suggestions on residential ISP's which you can recommend... I would like to get up to speed on this stuff.