The information on CO2 enrichment can be found all over the boards.

Your plants do need CO2 for respiration. Yes, they can have too much. If you are trying to supplement the plants with more CO2, that is doable and beneficial and will generally increase yields.

Your plants will only benefit from the extra CO2 if they are in ideal growing conditions, which I believe includes a higher ambient temperature. I believe that 1500ppm of CO2 is the optimum level, but can't say I know for sure.