Is the maximum tick granularity 1000 Hz? I tried setting that higher than 1000, but that caused issues with anything that used portTICK_RATE_MS (bunch of divide by ZEROs). Or am I overthinking this and needing to change the application of portTICK_RATE_MS? Let me know.
No you can make the tick faster than 1000Hz, but consider carefully if you really want to do this as 1000Hz is already fast, and the faster you make it the higher the kernel overhead will be.
You are indeed correct that going faster than 1000Hz will prevent portTICK_RATE_MS from working as the period will be sub 1ms. portTICK_RATE_MS is used for convenience in the demo applications, it is not used anywhere in the kernel code itself. Therefore, while setting the tick rate faster than 1000Hz would prevent the demo application tasks from working (without modification) it will not break the kernel itself.