I have started to build out twin rooms so that night air vents to the day room. I had friends that did it in Amsterdam and it worked wonders. They had huge buds.
All your stuff sounds so cool, but I agree the tank is the way, with the proper valves and gear. Too expensive for me. I think you need 2000 to 4000 ppm in the air and if too much the plants will hyper ventilate. My friends plants all puffed up and died cause he just let the co2 go without measuring.
CO2 is a known great additive, just how to deliver in an economic way. The pills in the water are not the way, it has to be delivered as a gas from above, not from roots up. The stuff I looked at were priced around 600 or so to really control it properly. They say it doubles the yield. Any first handers?