Welcome to our forum.
Let me be clear on what you are saying. If three of us spend an hour in the hot tub, then it will consume 10 and a half tea spoons of dichlor??? Surely that is as much as most use in a week.
I don't think i could use the cartridge that you mention because my filter doesn't have a centre section that comes off. It is fixed.I am encouraged to know that there doesn't have to be a constant reading of chlorine.My ozonator is always bubbling, even with the pump on.