It looks like you found a solution you are content with, but if you wanted to revisit this, I might have an answer to your user problem.
I, too, am running this on unRAID and I share many of the same experiences you’ve had with trying to follow the instructions in the official manual and responses from user posts and wondering why these commands or instructions don’t work for me.
In the post I link here, you will see that I removed the user parameter from the docker command and it worked. I don’t know why and I’m not going to ask. All I know is that the first time I it sat there for a long time, because my cron hadn’t run for a much longer time than yours. Now it runs in a blink every 5 minutes.