Thanks for finding an error in my instructions. The "For some reason" was that I had got a long hyphen (En-dash) instead of a short one in the code section saying
Daily reboot is not particularly needed. It's just generally a good idea on any computer running anything continuously, a good habit. It just ensures that any over-filling buffers get flushed, etc. And if something had gone wrong with Cumulus MX or any other running program (I run other things too on the same Pi), everything gets neatly restarted, so that problems get a chance to fix themselves eg if you are away on holiday.
To stop a Pi running Cumulus MX, you can just logon using SSH (eg, PuTTY) and type
and once all the lights stop flashing the Pi has stopped and you can disconnect the power.
If you don't want Cumulus MX to start when you plug the power in again, comment out the relevant line in sudo crontab -e before halting, and put it back in again when you do want it to restart.