Nice work!
There are additional tricks that might help in other situations. If you don’t need a main loop at all, you can call suspend_loop() at the end of setup. FreeRTOS will automatically put the system in System_ON_Sleep when possible.
Also, if you have an event based device (e.g. button press) with heavy main loop processing, you can use a FreeRTOS semaphore in the main loop. FreeRTOS will automatically put the system in System_ON_Sleep while it is blocked on the semaphore. Examples here: Getting lower power consumption on Seeed XIAO nRF52840