Well you certainly got futher than in the last discussion on this.
Controlling WS281X LEDs from Renegade? - Hardware - Libre Computer Hub
Just out of interest did you try to run the For loop with spi.open and spi.close within the loop ?
Do you have a sketch/photo of how you wired this up ? I would like to give it a try - for the fun of it and to be able to test my oscilloscope! Also were you following any particular guide ?
I do have a Pi running the Adafruit Neopixel library but my usual go to is an ESP 8266 or ESP 32 flashed with WLED for driving pixels - it’s so easy & cheap with more functionality that I will ever need !