Maybe this will help you. You can use ets_delay_us(stepper_delay); between steps. But, for example, every step 50 execute vTaskDelay(1);

or you can disable wtd in stepper task
esp_task_wdt_delete(NULL);
esp_task_wdt_delete(xTaskGetIdleTaskHandleForCPU(0));
in the stepper task before the infinite ...

You can see example how store struct at https://github.com/SergeyKupavtsev/nvs_component