its legit, I got mine, its just a little harder to find information about it. I had to email NORML because it wasnt on their website. if you want to grow more than 6 plants or start your own club its an easy decision for around two hundred bucks.
It feeds the beneficial bacteria and fungi in the soil that have a symbiotic relationship with the roots allowing your roots to absorb nutrients and water more efficiently, which in return makes an all around happier plant. It also contains trace amounts of minerals needed for plant life :)
I'd say shut off of the CO2 during the night cycle, and vent your room during that time and keep your room completely sealed while the lights are on to keep your CO2 levels up. last I heard, plants do not need high levels of CO2 during the night. hope this helps