Hi MJ –
This sounds like an exciting project! I would recommend using the Autopilot Greenhouse Master controller for environmental control: https://www.planetnatural.com/product/greenhouse-controller/. As far as cooling goes, you could plug either your portable air conditioning unit or your fan into the controller. From there, you can set your desired temperature for the thermostat to maintain in the room. For CO2, it would be best if you were to buy CO2 tanks from a local source. You would apply this regulator to the tank: https://www.planetnatural.com/product/co2-regulator-reg-1/, and regulate the levels with the environmental controller. The controller also allows you to program separate temperatures for day and night, which it sounds like you require!
Hope this helps!