IMO 1 bubble per 2 seconds is a good start point. Check your PH at the start and end of the light cycle it should be lower at the start due to the influence of the CO2 injection. I run my CO2 24/7 but have a power filter moving the surface at night to oxygenate the water. If I don't do this the fish are at the surface distressed. Most purists would advise that CO2 is stopped at night.

A compromise that I am about to try is the Barr reactor. This makes sense as in theory it vents CO2 without mixing significantly with the water.

I would leave all filtration active and have a constant surface movement without too much turbulance. KH 3 is the theoretical low point to avoid PH crash, in your case I would still increase the KH to 5 or 6 to give some latitude.

Check your KH and PH to work out the CO2 levels and adjust slowly to increase or decrease the levels. Above all watch the reactions of your fish, dead fish are not good for plants.

Ian