Great, glad this is working out. Thanks for helping out in the testing.
Not sure I fully grasped your post: is LOAD working right? It should be 1 LED for 0.15 of load, and 1 more LED each time it doubles (.15->1 LED, .30->2, .60->3, 1.2->4...). As you said, you can use 'top' to get the load number. Easiest to load is: 'openssl speed &' multiple times.
For TRAFFIC, it is the sum total of the number of packets per second on all 3 dc<n> interfaces. Kind of harder to really compute as there is a time factor to it, but a WAN download at 1MBps should give you a few LEDs. Again, it is packets per second, not bits/bytes per second.
For STATUS, SYS A should be on, and ARMED should blink.
For the tips, run 'ifconfig' to confirm there is a pflog0 device. Also, run 'pfctl -s rules' to list the firewall rules, and check if any of them have "log" in them. Every time a packet hits that rule, a blip occurs if it involves one of the dc<n>.
PS: I have a Firebox III, and this all works for me under Linux. I know for a fact that Firebox II's have a slightly different implementation for the control register to the LEDs, so I have not completely ruled out LED bugs just yet. Thanks for letting me know if your box behaves exactly as described above.