I use the same sort of inline reactor on my 75 gallon tank, and I am currently running about 4 bubbles a second or so. At the end of the day it drops my PH down to 5.6 no issue at all.
But as i am working out in other post I still have BBA, and im not really all to keen on test kits, they have never been helpful to me as of yet in doing anything that benifited my plants, how ever I dont think you should need to dump a TON of CO2 to get good saturation levels in the water, maybe consider the mist method? I dont really want the little bubbles all in my tanks but thats where I am considering going with my problems because I have heard people saying it works well and is more consistant...... good luck to you