CO² does have a cooling benefit to it. Problem is for the plant to get the most out of CO² you need to have the average temp around 88f. No exhaust only fans to move the air around. The humidity will rise as well it's best in the 70's for veg and only down to the 60's for most of the flower cycle. Drop it down to 45-50 the last 3 weeks of flower to force transpiring.

ziggy you need a slump pump switch so you can run any pump you want to. Or just get a slump pump that has the switch on it. The sell them at Harbor Freight tools, HD and Lowes as stock items.