I agree...I believe the only reasonable option to tweak would be:
Perhaps napi wasn't added until circa-Attude Adjustment (which is why my former devices used to crash under high load). I may test with snapshot, in order to be ready for production with the future release of OpenWRT 17.04.5 (or however it may be named).
I also recalled one more thing...LuCI!!! The IXP425 is a SoC (system on chip) and network CPU.
When logged out, I received much higher numbers. Using the same averages, ~100/100 as was displayed on the LuCI GUI.
I'll monitor (and prepare to re-flash)...