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Just tried your Wizards sequence out and it was great! Nice work. I didn't have an issue with the timing.
Some of the terminals will have multiple wires under the screw. I'm not an electrician though so consult one if you're not comfortable.
Did you purchase the relay suggested here? There is no limitation as far as I am aware. I've definitely had all 8 channels of the relay on at once. Perhaps you got a faulty one?
I've recently gone through this whole process (within the last few months). What exactly are you having issues with? Pretty much all you need as far as software is the OS and pygame, both of which are redily available.
You load and play the file by calling xmas.py. It would look something like: python xmas.py test.txt test.mp3